B-heptomino

The B-heptomino (or B-heptaplet, if the top-left cell is shifted one cell left) is a very common methuselah that evolves into three blocks, two gliders and a ship after 148 generations. Compare with Herschel, which appears at generation 20 of the B-heptomino's evolution. B-heptominoes acquired particular importance in 1996 due to David Buckingham's work on B tracks.

B-heptomino
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Pattern type Methuselah
Number of cells 7
Bounding box 4×3
MCPS 7
Lifespan 148 generations
Final population 28
L/I 21.1
F/I 4
F/L 0.189
L/MCPS 21.1
Discovered by John Conway
Year of discovery 1970

This pattern often arises with the cell at top left shifted one space to the left, producing a seven-bit polyplet that shares the same eight-bit descendant but is not technically a heptomino at all. Many conduits produce this form of B via the R-pentomino, so these two forms of B can be used interchangeably when marking in conduits.

The B-heptomino is considered a failed puffer or failed spaceship, since on its own it travels at c/2 for only a short time before being affected by its own trailing debris. However, it can be stabilized into a c/2 puffer or into a clean c/2 rake or spaceship. See, e.g., puffer 2, backrake 2, ecologist, or pufferfish.

In other rules

The B-heptomino is a stable puffer, spaceship, replicator, or oscillator in many non-totalistic rules. For example:

  • In B3/S23-e4e, it evolves into a (16,5)c/74 oblique spaceship.
  • In B3/S23-a, it is a glide-symmetric 10c/20 spaceship.
  • In B34ej5y6n/S23, it is an oblique quadratic replicator, one of only a few known.
  • In B36n/S2-i36c7c, it evolves into a glide-symmetric 9c/70 diagonal spaceship.
  • Generation 20 of the B-heptomino, showing its Herschel offspring
  • Generation 148 of the B-heptomino
  • A 6-cell parent of the B-heptomino
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See also
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