Wilson quotient

If p is a prime number, the quotient is an integer by Wilson's theorem; moreover, if p is composite, the quotient is not an integer. If p divides W(p), it is called a Wilson prime. The integer values of W(p) are (sequence A007619 in the OEIS):

W(2)=1

W(3)=1

W(5)=5

W(7)=103

W(11)=329891

W(13)=36846277

W(17)=1230752346353

W(19)=336967037143579

...

The Wilson quotient W(p) is defined as:

${\displaystyle W(p)={\frac {(p-1)!+1}{p}}}$

It is known that[1]

${\displaystyle W(p)\equiv B_{2(p-1)}-B_{p-1}{\pmod {p}},}$

${\displaystyle p-1+ptW(p)\equiv pB_{t(p-1)}{\pmod {p^{2}}},}$

where ${\displaystyle B_{k}}$ is the k-th Bernoulli number. Note that the first relation comes from the second one by subtraction, after substituting ${\displaystyle t=1}$ and ${\displaystyle t=2}$.

See also

• Fermat quotient

References

1. Lehmer, Emma (1938). "On congruences involving Bernoulli numbers and the quotients of Fermat and Wilson". Annals of Mathematics. 39: 350–360. doi:10.2307/1968791.

External links

• MathWorld: Wilson Quotient