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

Author

Christian G. Bower, Jun 22 2000

Keywords

• nonn

Links

• 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.

Extensions

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