A055915 Column 9 of triangle A055907.

1, 18, 164, 1050, 5367, 23232, 88125, 299992, 932849, 2685747, 7235237, 18392853, 44427807, 102552852, 227298680, 485679518, 1003915611, 2013360324, 3927664296, 7469755903, 13876848040, 25225619858, 44939663514, 78569415198, 134974052794, 228088973049

Offset

9,2

Links

Table of n, a(n) for n=9..34.

A. J. Guttmann and A. R. Conway, Hexagonal lattice directed site animals, Statistical Physics on the Eve of the Twenty-First Century, ed. M. T. Batchelor, World Scientific, 1999 (H_9 for hexagonal lattices Table 1).

Formula

G.f.: x^9*B(x)/((1-x)^19*(1+x)^9*(1+x^2)^8*(1+x^2+x^4)^6*(1+x^4)^4*(1+x^2+x^4+x^6+x^8)^2) where B(x) is g.f. of A055918.

Crossrefs

Sequence in context: A008418 A099196 A041618 * A208827 A327792 A071539

Adjacent sequences: A055912 A055913 A055914 * A055916 A055917 A055918

Keyword

nonn

Author

Christian G. Bower, Jun 22 2000

Extensions

a(31) corrected and more terms from Sean A. Irvine, Apr 09 2022

Status

approved