Restricted mini challenges Cop's Thread

Question

Robber's thread

Your task as cops is to select three things:

• A programming language

• An OEIS sequence

• A byte set

You are then to secretly write a program in that language that computes the nth term sequence using only the bytes in the set. You will reveal the three pieces of information so that robbers can try to figure out the program.

Answers will be scored by the number of bytes in the byte set with more score being good. Cracked answers have an automatic score of 0. If your answer is uncracked after one week you may reveal the intended program and mark your answer as "safe".

Answers must be capable of calculating every term in the b-files of the sequence, but are not required to calculate any terms after.

Sequences can be either 1 or 0 indexed for both cops and robbers.

Here is a Python Script that checks if your code matches the given byte set.

Answer 1

Haskell, A209229, (cracked)

11 characters (including newline):

s<=[ ]
how!

Outputs True/False as an indicator function for powers of 2:

1 => True
2 => True
3 => False
4 => True
5 => False
6 => False
7 => False
8 => True
9 => False
...

Inputs are positive integers.

Answer 2

Python 2, A000045 (Cracked)

ml:= input(as,forge)

^{it contains a whitespace and a newline}
Try it Online!
Intended solution

Answer 3

Haskell, A000045 (cracked)

I made up my mind, I think I like t more than s.

So let's use these 30 bytes (including newline) instead:

abcdeFgh|jklmnopqrtTuvwxyz
=()

Please note that the general challenge description demands that

Answers must be capable of calculating every term in the b-files of the sequence [...].

In this case, the b-file goes up to the 2000th number, which is way beyond what can be computed using Int.

Answer 4

Octave, A000290, Cracked!

The sequence is the square numbers: 0, 1, 4, 9, 16, 25, 36, 49 ... (so that you don't have to check the link).

'()/@^_

Answer 5

Haskell, A000045 (Cracked)

Everyone likes Fibonacci numbers, I like Haskell...

I have carefully selected 30 bytes for you: the lowercase letters except f, i and t, you get the uppercase letters F and T and the pipe symbol | instead, and the three symbols =(), and newline. Here they are again:

abcdeFgh|jklmnopqrsTuvwxyz
=()

Answer 6

Haskell, A034262, 43 bytes, cracked

!"#%',.=?ABCDEFGHIJKLMNOPQRSTUVWXYZ[]_{|}~

Computes a(n) = n³ + n.

Answer 7

Haskell, A009056 (cracked)

Another simple one, now again with enough letters to make it look like ordinary Haskell and maybe for you to amaze me by finding a solution completely different from mine.

The sequence is Numbers >=3 and the charset consists of these 30 bytes:

{[abcdefghijklmnopqr uvwxyz]}.

---

The crack has some nice techniques. I was just thinking of this:

head . flip drop [ floor pi .. ]

Answer 8

C (C99), A000005, 25 Bytes#, Cracked!

These are the bytes for a full problem, takes n as a command line argument and outputs answer to stdout.(Space is included in bytecount).

<=>,;!"()*%+acdfhimnoprt 

Answer 9

Unary, A002275, 1 Byte

Byte set:

0

I had to at least try it :3

(I don't think it will be particularly hard seeing as every command in the language is available)

Answer 10

Cubix, A000027 (SAFE) 17 points

!&')-/0;@Oiru.NSQ

My solution:

!O!;i)!/u&!!r-)0'u;;!@

watch it online here

I originally did this without .NSQ but I figured I could add them safely.

Explanation:

This sequence is just "The Positive Integers". However, Cubix has three input commands, i, which reads in a single char (pushing -1 if input is empty), A, which reads in the rest of the input as chars (pushing a -1 to the bettom of the stack), and I, which reads the next number off the input (pushing 0 if there isn't a match). So naturally, I only provided i which reads in digits as their ascii value. uh-oh. Additionally, -1 is the usual marker for end of input, in conjunction with ? so I got rid of ?, forcing me to use ! (skip next instruction if TOS is not zero) for control flow. Finally, I thought I needed & to concatenate digits for printing with O (which outputs the top of stack as a number), but I realize now that that wasn't necessary either!

Another part of the challenge was originally to not have . the no-op character, but you can use pairs of ! instead if you're careful:

    ! O
    ! ;
i ) ! / u & ! !
r - ) 0 ' u ; ;
    ! @
    . .

i) : read input, increment.

!/ : if top of stack is zero (end of input), turn left

left: ;O.@ : pop top of stack, output as number, halt.

otherwise:

u'0: push char code of 0 to top of stack

)-r: increment, subtract, and rotate

;; : pop top of stack twice

u& : concatenate digits

!! : net zero effect, now we are at i) again.

Answer 11

Hexagony, A057077, 77 bytes

Periodic sequence 1, 1, -1, -1. As a list:

a(0) = 1
a(1) = 1
a(2) = -1
a(3) = -1
a(4) = 1
a(5) = 1
a(6) = -1
   ...

Character set (edited), which includes a newline and a space character:

!%&(),0123456789;?@ABCDEFGHIJKLMOPQRSTUVWXYZ^abcdefghijklmnopqrstuvwxyz[]#. 

Try it online!

Answer 12

Perl 5, A000030 (Cracked)

Byte set:

imnprt7 $;()<>=~.

Try it online!

Answer 13

JavaScript (ES6), 17 bytes, A000290 (Cracked)

Again, this is the simple square sequence a(n) = n².

Byte set:

$()=>CI`abelotv{}

Answer 14

Seed, A005408 (Odd Numbers) - Safe

Here's a slightly more challenging one. You may use any characters valid in Seed:

[0-9 ]

You shouldn't be able to brute force this one in a week unless you have a monster of a computer. Good luck! It's crackable.

Hint

This is the Befunge-98 program used in my solution: 9&2*1-.@ (the 9 can be removed, but my solution just happens to have

Solution

8 47142938850356537668025719950342285215695875470457212766920093958965599014291682211474803930206233718243166021324700185443274842742744297183042397910454208210130742260519105651032450664856693714718759816232968955289663444878636053035645231246428917992493766505872029989544065894418166685284738859999912471659057565000392419689361271972485444731284404987238803115210428572945108908191097214978382112218242627719651728712577306652405452922782307249485947045215982784790396555726144526602778473387279897334709142853151393812930171163300904436548870603006549005515709074682843356844201220668045057407146751793470423217099467145255174198241606814578351260769359571053755888106818197239116973006365593563235361647743411341624822052103816968153274122434280200888824954875622811325064255818154979564925710534165572852442761249176778416688044630942040966271963723430245979221181930857841829694362184653939393940015797332978459794253176110314873994228261888801228999293570329618551223457182420746927212801550646743152754821640064626761542582557138452651970009253770914346130172884305622027370793496993281847017017643506435562229916984107083951938286577012273222191422054315198157936674247934699496471202544270325061352014830137178245082445717253260177560449757186762445707057028987371278573629077370632470496186218574320801798046510846708620502139560277546345198686675095078255875594169064796673074708822106659920187882062247609587560174781170641367430722951002242213604709887062481149928551745163110045572994991844223216663621203042075294195007458339984527333125093390189721042315604498435269143549420166732177200370228527273606218617171975362431824163269672003982537382982066136613799403024924018145511099557720492305303748099327810811511080314262364010281851651151072957475365629128068033597559560186625877942054704386175359499573139930378099420149452745731809033737756051947913924265484582800618244473333957173960222243311738522875022546610298627492222587971756897328087719407454153248557203886421828643453889090192355970705084245312184441674098515659253482621260617211786550204852895652236768886852209506535523414991099331857674826373947830587028494510697603296607361093480842935154672353288419699354739650168309017848485131553416956405911683526896232046773861961911767319373432460217755874481607587604361758089936007730253450733375831228127106295259261723611771334468553746160739548375950046831923765023329346333968732796413192682936767133122325481273354810124729664400173367781325488656859581438769940474229394692089519981810909719628263357284973442177568041416363386891516725592952892168077523560584005586276794967492051823290615767599202657060820223928678900774601616908031321346819422162123048834532926372862962159255934240435694566497798544870186550219886342379298214007368081326725550763589917206162393892085506551547475259270513853987294911388226039365971184089828739349642347312302559286882065147953715607221387657413593069535573044067517274676745306396611760657091792151803798859781616126637075577936361782593546481811651450365118155866449850474140044293772144065341051900055416408240857348697564252386403719942197789892382627153382011984996644288495699209129097948405810551134169739499539470610790009272281731894550593600643079188663110695127017324336488487580799309995227054576681630676222848231145106058050452439356753552872060820230589152143268436210090733908507724084889788244157692417246691477400856716677564609725979550100138132944851304473466485128295568194188600539248624248078558656162635444219199062786468487219220160009464328883337821175254405764395407405891483810757405446047244460754827113527540703326714751461178900155717130399854358953609995319006890674085682111514072508440632941090209366005504352890092326935445829213294943731517698438648298921337375443947066950275955144209037675013663600062205168551851984361951824731229113379464426979717688372371011461890139087487634586087688796134318950140718824105959727161482389914414206768064990410615468858520426399188835467970981786227122743162945627167772066100574532803061925537235491026486409948728571706557098859331941260622260924660292578136091523126589085799981416326395824628987154802653126685882440760385315869346960183809644486238810912663304360284449610976505715001267334297285036791711464142665122000857666018757370925847113798258537503747803972255591351740843663253694303946089997282812556281486820325652814785261116697261899511762129550421005941055852897451832731304151488058522478260009347144486599715629242208891126238083949281490804191584238425634093683587199278186505945727829025071885767559828670803412582690901456978557379916793144695491189633486065077294485660840922713748873840986104486221528464294334436081663106336911265802650605150347413103936140565054608396116572669757269475369570465915381045895991937087068526458273755454602799814909213983801968791431574508976448235055061998715636460946550584682626461010298101802277643570201189324102499951196290880892383380284543173390448406975616650185808619832614403133944687275834716343817926764699295672501869876060896683204343897481630037607159476461359111190545646447421653872016775582115425356868533678655969328210255235050133718364831289991244684695035034122861927276046255405376531096051541299607470934463981741370397268760811035606321455156217990078359217247117349544774085111287345436916077577032709684005131011429476229617901273007027774182864475737502587896225475248267937497254066190335088823904767397814233350286976811901982274477445433872253983823904938249655089770642137858608313524715533520654523880832056453080193644871440738737277389718589793074725139142291918837706550037934799585495183374639955887618135803388399608755212147742199481865453122900714456703147150994585431640652462593333773031385396586933380738103697887063571042512186708015948688088011290197524699274772775288900864690592106393483764109837848793374117655194139018455509931621247697015323332300969105814058088442693320033876473960017819576425062784644138417943454576404265382986995583045527928832

Answer 15

Haskell, A000045 (cracked)

It's cracked, and I won't start a new version, but if you want to play more: it's possible without y, and it's possible to be efficient.

---

I apologize for leading you in wrong directions by giving a g. Let's do the same without!

Here are the 29 remaining bytes (including newline):

abcdeFh|jklmnopqrtTuvwxyz
=()

Again, remember that Int won't be enough to compute the 2000th Fibonacci number which is needed because it is in the b-file.

Answer 16

Haskell, A000045 (cracked)

This is kindof (as announced) not a new version, but completely different. (Right?)

I still hope I can make you rediscover my nice little observation.

This time you are asked to implement the Fibonacci sequence using a charset of size 17, which (as far as I know) contains only one two unneeded chars:

eilnt=(,).[ ]_:0!

Note that there is no newline (but feel free to show a version which has them for readability) and remember that you have to be able to compute the 2000th Fibonacci number.

Answer 17

Braingolf, A010701 Score: 9 [SAFE]

Byte set:

0x21, 0x24, 0x2F, 0x3A, 0x3F, 0x5B, 0x5D, 0x5F, 0x7C

Try it Online!

The code:

$_/[!?:]|[!?:]|

Try it online!

Explanation

$_/[!?:]|[!?:]|  Implicit input from commandline args
$_               Remove top of stack
  /              Niladic division, push 5
   [...]         While loop, decrements bottom of stack at start of loop
                 then decrements each time loop reaches end
                 Exits when bottom of stack is 0
    !?:.|        If conditional without popping, runs contained code if top of stack is 0
                 This is the sneaky trick here. The conditional skips the end of the loop
                 As a result, this whole block from [ to | effectively acts as a decrement.
         [!?:]|  We do this twice to lower the 5 we pushed down to 3
                 Implicit output of top of stack.

Answer 18

cQuents, A000217, Cracked

Byteset:

$:=1;
\-

Note that this uses a feature that I haven't pushed the documentation for yet, so I'll push that tonight, if you wait until then. (Or you can slop through my source code... have fun). Documentation pushed. Would be a byte less if a recent bugfix was on TIO.

Intended solution:

=1-1:--\1$ ;$

Try It Online!

Answer 19

R, A000142, (Cracked)

Byte set:

-()*,`=cfinotu

Intended solution:

f=function(n,c=n==n)'if'(n,f(n-(n==n),c*n),c*(n==n))

Answer 20

Python 2, A000045 (Cracked)

l:= input(a,forge)[]

^{it contains a whitespace and a newline}
Try it Online!
Intended solution

Answer 21

PowerShell, A000012, 19 bytes, SAFE

$.0=[]acefilnorstv

Includes a newline and 18 other bytes. Good luck.

Try it online!

---

Intended Solution:

$a=$a[0]
$error[0].invocationinfo.offsetinline

Try it online!

This sets $a to be the value of an uninitialized variable $a indexed at [0]. Since that won't work, you get an error stating the following:

Cannot index into a null array.
At line:1 char:1
+ $a=$a[0]
+ ~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : NullArray

The second line then pulls the .InvocationInfo and .OffsetInLine (i.e., where the error occurred), which in this case is always 1, and hence the A000012 sequence.

Answer 22

cQuents, A000027, Cracked

 !"#%&'()*+,-./0123456789:;?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~

That's right! You get all of ASCII! Wait... there's no $... what's $ again in cQuents? Oh, yeah, the index builtin. Well, tough luck :/

Intended Solution:

#|A:A

Try it online!

Answer 23

CJam, A000042, cracked by Lynn

Byte set:

{})_%si

Answer 24

R, A000290, (cracked)

Byte set:

()%cfinotu

Answer 25

Ruby, A000004, 5 bytes, Cracked

Just messing around to start off. Should be easy for anyone familiar with Ruby. It's a low score, but whatever.

/np.$

---

Cracked, unintended exploit

Cracked (intended answer using n flag)

Answer 26

Python 3, A007504 (Cracked)

This byteset, including newline:

bfuwo)nm1h[=(t+;0a
sig%pr, le:]

My code does not provide infinite output, but can compute the entire b-list.

Answer 27

JavaScript (ES6), 13 10 bytes, A000045, Cracked

This should be easy.

This is the Fibonacci sequence: F(n) = F(n-1) + F(n-2) with F(0) = 0 and F(1) = 1.

Byte set:

$()-:<=>?[]_~

Edit:

It can be even done with the following 10 bytes:

$()-:=>?_~

Answer 28

Snowman, 212 bytes, A000042

#$%&*01:;=?@CEFGHIJLMOQUVXYZbcdefghijlmnopqsuvxyz~

... plus space, 0x00-0x1f inclusive, and 0x7f-0xff inclusive.

Answer 29

Python3, A008615, Cracked

Bytemap (with newline):

n)ir=-
(u0*pt

Answer 30

R, A105311, (Cracked)

Byte set:

'%(),:=acdegilnopstx

Answer 31

R, A105311, (cracked)

'%(),:=acdeginpstx

Let's try this without the l or o.

Since this has been cracked, the intended solution:

cat(diag(diag((a=scan()))%x%diag((a==a):a)),sep=''). diag is an interesting function, that can be used in three different ways. When presented with a single integer (diag(n)), it creates a NxN matrix with 1 on the diagonal. When presented with a vector (diag(1:n)), it creates an NxN matrix with the vector on the diagonal. When presented with a matrix (diag(diag(n))), it returns the diagonal as a vector. %x% computed the Kronecker product of two matrices, where each element in matrix 1 is multiplied with each element in matrix 2 separately. Doing this with a length n identity matrix and a 1:n diagonal matrix, creates a length n^2 diagonal matrix with 1:n repeated n times. diag extracts that again, and cat prints.

Answer 32

Befunge, A000142, 29 Bytes, (Cracked)

Byte Set: @.$_ ^*:\v>-1&

If you can't tell, that Byte set includes a space.

This should be moderately easy to solve.

Edit: Forgot the "A" before the OEIS

Answer 33

R, A057077, (cracked)

1, 1, -1, -1, 1, 1, -1, -1, etc

Byte set:

()*/=2abcinopst

0-indexed.

Answer 34

C, A027868 (Cracked)

I don't expect this to last too long...

Byte set: int (){reu<5?-:/;}

Answer 35

Python 2, A000142, cracked

Probably not too difficult, but since I really enjoyed solving these I thought I'll be a cop for once. Here's the byteset (first one is a space):

 ()*-:=abcdfghijklmoqruwyzABCDEFGHIJKLMNOPQRSTUVWXYZ

Intended solution

LyricLy's solution is much cleaner, but here's the one I had in mind:

Basically it's the same but instead of using bool(r) for 1 I used (r-r)**(r-r): f = lambda r: (r==r-r or r==(r-r)**(r-r))*(r-r)**(r-r) or r*blam(r-(r-r)**(r-r))

Answer 36

CPython 3.6.2, A000002 (cracked)

I don't want anybody running out of single-character variables, so I'm giving you 70 pseudo-random characters courtesy of Latin-1.

·èõÉÀ]ýÜâô¾×l¡¿Ós¦Í½²uÊi´#¬©Åñ[);?ò
à¢ådêøóÎÐþÒÏ®,(Öß.=Õc_ö\§éºún$tÞb¨

This is evil. You can't make a for loop. You can't make a while loop. You can't even try to do anything, much less except. I have given a new line so that you can use more than one statement, but there aren't any spaces, tabs or even colons to let you use any sort of flow control. There are no numbers. There are no strings. There is nothing of any use.

You do have \ and #, though, so you can write clear code with soft breaks and comments.

That is, if you speak Jelly.

Answer 37

JavaScript (ES6), A000035, cracked

A000035 is n mod 2, in case the site goes down or you're too lazy to check yourself. Charset:

023456789\`efu

Taking the "somehow still Turing-complete" route. I suppose I could've added 51 or so non-ASCII chars to improve my score, but that feels kind of like cheating.

Takes input through prompt and outputs through alert, and can be run in any modern browser.

---

Intended solution:

\u0046\u0075\u006e\u0063\u0074\u0069\u006f\u006e`\u0046\u0075\u006e\u0063\u0074\u0069\u006f\u006e\u0028\u0046\u0075\u006e\u0063\u0074\u0069\u006f\u006e\u0028\u0022\u0072\u0065\u0074\u0075\u0072\u006e\u0028\u0034\u0038\u0032\u002f\u0032\u0029\u002e\u0074\u006f\u0053\u0074\u0072\u0069\u006e\u0067\u0028\u0032\u0032\u0029\\u002\u0062\u0027\u0065\u0072\u0074\u0028\u0070\u0072\u006f\\u006\u0064\u0070\u0074\u0028\u0029\u0025\u0032\u0029\u0027\u0022\u0029\u0028\u0029\u0029\u0028\u0029```

which, when the escapes are removed, translates to

Function`Function(Function("return(482/2).toString(22)\u002b'ert(pro\u006dpt()%2)'")())()```

which simplifies again to

Function`Function(Function("return(482/2).toString(22)+'ert(prompt()%2)'")())()```

This works because JavaScript allows \uXXXX escapes in variable names (though not in arbitrary code, as Java does). The outer Function`code``` is necessary to run the code at all, since the entire thing needs to be escaped.

(If you're confused about how this works: JavaScript has something called tagged template literals, which for our purposes is just a function call on a string; it just uses f`string` instead of f("code"). So Function`code``` is about the same as Function("code")().)

Now, because of the lack of the hexadecimal chars 1abcd, we'll have to double-encode certain necessary characters such as the m in prompt(). So instead of \u006d, it becomes \\u006\u0064. But now we need to evaluate this as a string twice to make sure this gets fully decoded. (pro\u006dpt() would work just fine, but using \u002b as + would not.) This is what the second Function(code)() is for.

One further obstacle exists: there's no 1 in the charset, necessary to create an a from \u0061. So there's no way to generate an a by unescaping a string (I checked, the octal representation is \141). Instead, we can generate it with e.g. (20/2).toString(20). I went ahead and generated al in this manner because l would require double-escaping like m.

But the problem now is that the innermost Function call is now just generating a string. In order to actually execute it, we need to return it from the function and pass it to a third Function call. This we do, and finally our journey is complete.

^{*I am aware of using ${} within template literals, but those aren't in the charset, alright?}

Answer 38

Cubically, A016742 (Cracked)

This sequence is even square numbers: 0, 4, 16, 36, 64, ...

Byte set:

• Any letter except [UuDdLlRrFfBb]
• The digits [6789]
• Any symbol except [-^:@/]
• Anything not mentioned in the ASCII character set, including whitespace.

Try It Online!

Answer 39

Python 3, A000002, Cracked with the intended solution

These are the bytes of a full program, 0-indexed solution for the Kolakoski sequence: OEIS A000002.

pg*rn:e+%2a tu]
(=foi[)1l,

This contains a space, a newline, and all the other characters in the snippet above. Hopefully this won't be too easy to crack :)

Answer 40

Python 2, A000042, 11 Bytes (Cracked)

Byte set:

int(pru*1)'

Answer:

print '1'*input()

Note: This is my first ever answer on PPCG, and I may have made a mistake...

Answer 41

cQuents, A033307, Safe

Fe_pz:"/`'-2;

Try it online!

Explanation:

":z--F_p-2
Try it online! ": means a char sequence; basically, the output needed. Now, we need to just get the current index, which would usually be $. z starts out as 0 and is the previous number from then on, so we need just to add one to it. -- is the equivalent of +, and F_p-2 means Floor(Pi-2), which works.

Answer 42

JavaScript (ES6), 4 bytes, A005408 (Cracked)

This should be an easy one. Odd numbers: a(n) = 2n+1

Byte set:

$+=>

Answer 43

CJam, A000142, 8 bytes, Cracked

Byteset: {}*+)%1\

Answer 44

Python 2, A006577, Cracked

Byte set:

+s-t,n u
r)i1(d>]f[:e&

Shouldn't be too hard, but still fun.

EDIT: Cracked by @BruceForte. The crack looks just about identical to my crack, but here's mine for reference.

Try it Online

Answer 45

Python 2, A001146, Cracked

Byte set:

print(2*u)

Answer 46

Unreadable, A000027, 92 bytes, Cracked

Byte Set:

!"#%&'()*+,-./0123456789:;?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~

Also add space and newline

Answer 47

LOLCODE, A000290, Cracked

Byte set:

.12ABDEFGHIKLMNOPRSTUVXY

The byte set also includes space and newline.

HAS FUNZ!

Answer 48

Perl 5, A007094 (Cracked)

Numbers in base 8

Byte set sub {if($_[1]!=%/)ret-n;}

Try it online!

Answer 49

Octave, A000045

This produces the Fibonacci numbers, OEIS A000045. There's both a space and a newline in there.

It's 0-indexed, so input 0 gives 0.

 ()-;=>cdefinotu

Answer 50

JavaScript, A000004 (Cracked)

Look from the other side

at~N+1

Step Hen's solution

~NaN+1

My solution #1

~1+1+1

#2

~~NaN

Answer 51

Ly, A005150, Cracked

!$+-012<=>JS[]lnprsu

Well. Let's see how this plays out.

Answer 52

dc, A028444 (cracked)

-?/*+23568dpr

There are no spaces in the byte set, but that’s not a big deal for dc.

Sequence is indexed at 0.

Note: Rado’s Sigma function grows faster than any computable function and is thus noncomputable!

Intended solution: ?dddddd***3*rdd**22*-rd*53*+r26*-8/p

Answer 53

CPython 3.6.2, A000796 (cracked)

I like Latin-1. Here's another 70 characters.

,Ðûô[u÷ÎÆ»énb¤Äö]?có´å¡ùÇõÓ«;Ñ$èñÙdÁ¼
¢üÔltsð½(þÚ#ä.×çÈýŧã¯\)³íï¬Â±¥_Ê=iÌ

This bunch of characters can calculate the decimal digits of pi. Surely this requires flow control. And yet there isn't a colon, so that is impossible. You can't even eval a string when there is neither eval nor a string.

I'll give a hint: my program takes input from stdin and outputs to stdout, but I am almost completely certain that it is possible to use other I/O methods.

Answer 54

R, A000027 (Cracked)

An easy one to warm up :)

Byteset:

eiytnd

Solution:

identity returns the input, so maps n to n.

Answer 55

Python 2, 24 bytes, A001246, cracked

Byte set:

 )(+*-/12:=<acbdfmlonrx

Try it online!

Answer 56

Python 2, 21 bytes, A157433, cracked

6ut1 28rp5=)ni+03(*7

Try it online!

Original solution:

n=input() print 128*n**2+2336*n+10657

Probably super easy, but eh, I have =).

Answer 57

Jelly, 16 bytes, A000042 (Cracked)

Byte Set:

%1@JOiv¤ØȷḌṁị“”€

(The two quotes are different: one is opening and the other is closing).

(uses Jelly codepage)

The sequence is: a(n) is the unary representation of n.

Answer 58

Python 3, 19 byteset, A000290, Cracked

This is the perfect squares: 0, 1, 4, 9, ....

Byteset:

(fam, l+db-ise=10:)

Note: I had two iterations with duplicate characters (and missing characters) because I'm dumb.

My solution (not very efficient):

f=lambda l,a=1,b=0:f(l-1,a+1+1,b+a) if l else b

Try it online!

Answer 59

MATL, 11 bytes, A000984

Uses some of these bytes (ASCII):

$&)+/:HZdep

Due to floating-point precision, results are only guaranteed to be accurate up to the 26-th term. I hope that's acceptable.

Answer 60

Ruby, A000217, 15 bytes, Cracked

Uses the -p flag to take input from stdin and output to stdout.

$mu.to_vim[d=s]

Intended solution:

$_=[$...$_.to_i][$..div$$].sum

Answer 61

JavaScript (ES6), 10 bytes, A000007

Byte set: -)$>yRa=A(

Answer 62

Seed, A000027 (Counting Numbers) (Cracked)

You may use any valid character in Seed:

[0-9 ]

Have fun! The resulting Befunge program is short, so you should definitely be able to brute force it within a week (if you're crazy enough to do that).

My Solution:

My solution is a little bit longer than Lynn's solution...

4 47142938850356537668025719950342285215695875470457212766920093958965599014291682211474803930206233718243166021324700185443274842742744297183042397910454208210130742260519105651032450664856693714718759816232968955289663444878636053035645231246428917992493766505872029989544065894418166685284738859999912471659057565000392419689361271972485444731284404987238803115210428572945108908191097214978382112218242627719651728712577306652405452922782307249485947045215982784790396555726144526602778473387279897334709142853151393812930171163300904436548870603006549005515709074682843356844201220668045057407146751793470423217099467145255174198241606814578351260769359571053755888106818197239116973006365593563235361647743411341624822052103816968153274122434280200888824954875622811325064255818154979564925710534165572852442761249176778416688044630942040966271963723430245979221181930857841829694362184653939393940015797332978459794253176110314873994228261888801228999293570329618551223457182420746927212801550646743152754821640064626761542582557138452651970009253770914346130172884305622027370793496993281847017017643506435562229916984107083951938286577012273222191422054315198157936674247934699496471202544270325061352014830137178245082445717253260177560449757186762445707057028987371278573629077370632470496186218574320801798046510846708620502139560277546345198686675095078255875594169064796673074708822106659920187882062247609587560174781170641367430722951002242213604709887062481149928551745163110045572994991844223216663621203042075294195007458339984527333125093390189721042315604498435269143549420166732177200370228527273606218617171975362431824163269672003982537382982066136613799403024924018145511099557720492305303748099327810811511080314262364010281851651151072957475365629128068033597559560186625877942054704386175359499573139930378099420149452745731809033737756051947913924265484582800618244473333957173960222243311738522875022546610298627492222587971756897328087719407454153248557203886421828643453889090192355970705084245312184441674098515659253482621260617211786550204852895652236768886852209506535523414991099331857674826373947830587028494510697603296607361093480842935154672353288419699354739650168309017848485131553416956405911683526896232046773861961911767319373432460217755874481607587604361758089936007730253450733375831228127106295259261723611771334468553746160739548375950046831923765023329346333968732796413192682936767133122325481273354810124729664400173367781325488656859581438769940474229394692089519981810909719628263357284973442177568041416363386891516725592952892168077523560584005586276794967492051823290615767599202657060820223928678900774601616908031321346819422162123048834532926372862962159255934240435694566497798544870186550219886342379298214007368081326725550763589917206162393892085506551547475259270513853987294911388226039365971184089828739349642347312302559286882065147953715607221387657413593069535573044067517274676745306396611760657091792151803798859781616126637075577936361782593546481811651450365118155866449850474140044293772144065341051900055416408240857348697564252386403719942197789892382627153382011984996644288495699209129097948405810551134169739499539470610790009272281731894550593600643079188663110695127017324336488487580799309995227054576681630676222848231145106058050452439356753552872060820230589152143268436210090733908507724084889788244157692417246691477400856716677564609725979550100138132944851304473466485128295568194188600539248624248078558656162635444219199062786468487219220160009464328883337821175254405764395407405891483810757405446047244460754827113527540703326714751461178900155717130399854320238635234164429884664271159504714368008455653061601459723385727262777232764564573673873772208222457183846136405752956618693937985108892893985455752900109747276359722218661153262749015305405756329658744441481575547254529963547290233424398012124166511178581644295375904189900373061373853471489496222876806462541916199940534855562482928962080779491332702863921351256172643450743469939804784306286205587292552998145733381435925702081855362374409244827640579395543246453123597643190692540938806013686596772963034314363354010871521973403725835700408947963387110274004628480425371734331910891935140460595015189156420163115488068088520486798706569490006916112796733633895122682258059129006594304004203161927532260544237735899697152969940248758172957772287759336801595261613720119580891726456931895143417855893848415813470404827691913198395587019754512910027895295524122640301750273229263700158423422494600783294301471077720755163088097928474808200825811331834384330131090616226795924514158947235407965623454021092089105236025774499670509312408897668570458845620423145441557589436789713088947243846896823513743795131462439985465454654508125778329519910755888052092925306512948187971238329609568930378458165199920437525216462470929107070404811453630873763646812061350580161443056020563505260186672704841049972564837245044063297483792279875783885332694312955039151703943626840229495942158368887321883672956326501715270278543111513846830331160757034936022626603927067201550075630055296060821698451711220226998542584472966056248420845670285305975196992649811350779376980410458954534606441616709943508562093877902996409050522302853982991210150961788557227893313889825011281746787557452112185337922107257901043776646541934164147921577497411930472664026894384833716916001510862714001082105916461354489145794983975342462583664139916994875750562786683033654066234795041967161156949148282294752956521537053912878502375506909313842856133697079387338725355753694963250928996068864246591064004864326952187480597051907196284596345012237848475736570739686898404311769576575237233438553293161482584973742517010294566986396986963333792493710800886286588229647009335037917560300340277732774595016553407284174237194411762775063365955286488230300605484062176178336345135677894004813511507360069468591733327248913533084977745451497662084575239380871947004076480854627777980299105041121280

Answer 63

C, A000312 (cracked)

-,;:?(){} eglnortu

The specs call for a complete program, however this would add many more characters to the byte set making the challenge trivial. Instead, you’ll be providing the code within this template:

«your-code-composed-of-characters-in-byte-set»

#include <stdlib.h>
#include <stdio.h>

int main(int argc, char** argv)
{
    int n = argc > 1? atoi(argv[1]): 0;
    printf("%d ^ %d = %lld\n", n, n, «your-function-name»(n));
    return 0;
}

Note that your code comes before the #includes.

Answer: long long l(long long o,long long n){return o- -n;} long long o(long long n,long long g){return g?(--g?l(o(n,g),n):n):g;} long long n(long long g,long long l){return l?o(n(g,--l),g):- --l;} long long g(long long l){return n(l,l);} Addition l is expressed as subtraction of a negated value m + n = m − (−n), multiplication o as a series of additions m × n = m × (n − 1) + m, exponentiation n as a series of multiplications mⁿ = mⁿ⁻¹ × m, and finally the function g which calls the exponentiation function. On machines where long long is 64 bits wide, this code will give incorrect answers for n ≥ 16, but note there are machines out there with word lengths of more than 64 bits, e.g. the Ethereum Virtual Machine (EVM) with 256-bit words where long long could naturally accommodate values ≫ 2⁶⁴. So in theory the code would work for n ≥ 16.

Answer 64

Haskell, A001107 (cracked)

This one is easier, the sequence is growing slower and the charset is smaller.

Compute the decagonal numbers n(4n-3) using the following charset of size 9:

.,_-=[ ]!

Again there is no newline.

Answer 65

CPython 3.6.2, A000720 (cracked)

I have decided to squeeze as many characters out of Latin-1 as possible without simplifying the challenge. There are some unprintables, so I will provide the characters in the following format:

print(",".join((
    "0x0-0x8",
    "0xa-0x1f",  #inc. \n
    "0x23-0x24",  # chars #$
    "0x28-0x29",  # chars ()
    "0x2c",  # char ,
    "0x2e",  # char .
    "0x3b",  # char ;
    "0x3d",  # char =
    "0x3f",  # char ?
    "0x41-0x5d",  # A-Z and chars [\]
    "0x5f",  # char _
    "0x62-0x64", # chars bcd
    "0x69",  # char i
    "0x6c",  # char l
    "0x6e",  # char n
    "0x73-0x75", # chars stu
    "0x7f-0xff"
)))

I think that makes 208 characters. Feel free to use any of these.

I did not hard-code; that would take so many characters I would have to start meta-meta-programming. This set of characters is provably Turing-complete.

Answer 66

shortC, A000240, 64 bytes

Uses the characters in this ASCII map:

    "     %     ( ) * + , -     
  1 2                       >   
@ A         F     I             
    R   T             [   ]     
  a     d         i         n o 
p       t     w       {   }    

Map credit: ETHproductions

Answer 67

Python 2, A005150 (Look and say), safe

 "()+,.01:=ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]_celnortwx

Gee, you don't didn't have much, do did you?

Intended solution:

exec("FROM ITERTOOLS IMPORT GROUPBY\nA=\"1\"\nFOR _ IN RANGE(1,INT(INPUT())):\n\tA=[\"\".JOIN(GRP)FOR M,GRP IN GROUPBY(A)]\n\tA=\"\".JOIN([STR(LEN(X))+X[0]FOR X IN A])\nPRINT(A)".lower()) You have all of the uppercase characters, and just enough lowercase ones for \n, \t, exec and lower.

Answer 68

Javascript (ES6), A000079, 6 Bytes

[]()+!

Hint:

Intended solution is 25496 characters long.