A153986 Number of planar n X n X n binary triangular grids symmetric under 120 degree rotation with every one adjacent to exactly 2 other ones.

1, 1, 2, 2, 2, 4, 9, 15, 37, 88, 191, 729, 2246, 6555, 31434, 144150, 601688, 3970089, 24322158, 135488789, 1251604698, 10410417129, 79632436378, 997602199170, 11483571472544, 120898733308159, 2073714604283068, 32605974669636948

Offset

0,3

Links

Table of n, a(n) for n=0..27.

Crossrefs

Sequence in context: A274076 A160179 A021822 * A199889 A293177 A231382

Adjacent sequences: A153983 A153984 A153985 * A153987 A153988 A153989

Keyword

nonn

Author

R. H. Hardin Jan 04 2009

Status

approved