OFFSET

0,3

COMMENTS

The D-toothpicks placed in northwest or northeast direction both are prohibited, except in the substructures in which the symmetry could be broken, so a(44) = 509, not 507. For another version with broken symmetry in some substructures see A233764. See also A231348, a simpler cellular automaton based in triangles which has essentially a similar structure.

A233781 (the first differences) gives the number of toothpicks or D-toothpicks added at n-th stage.

First differs from A169780 at a(24).

First differs from A233970 at a(25).

First differs from A233764 at a(44).

LINKS

CROSSREFS

KEYWORD

nonn

AUTHOR

Omar E. Pol, Dec 15 2013

STATUS

approved