A055912 Column 6 of triangle A055907.

1, 12, 74, 331, 1212, 3829, 10778, 27651, 65745, 146663, 309831, 624423, 1207701, 2252494, 4067393, 7134576, 12191298, 20342987, 33217622, 53174235, 83580380, 129177701, 196557754, 294776792, 436141322, 637204826, 920020667

Offset

6,2

Links

Table of n, a(n) for n=6..32.

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_6 for hexagonal lattices Table 1).

Formula

G.f.: x^6(1 + 5x + 13x^2 + 40x^3 + 85x^4 + 160x^5 + 297x^6 + 453x^7 + 711x^8 + 956x^9 + 1276x^10 + 1614x^11 + 1798x^12 + 2192x^13 + 2064x^14 + 2446x^15 + 1949x^16 + 2220x^17 + 1546x^18 + 1642x^19 + 1011x^20 + 959x^21 + 558x^22 + 427x^23 + 249x^24 + 135x^25 + 85x^26 + 32x^27 + 15x^28 + 8x^29 + x^31)/((1 - x)^13(1 + x)^6(1 + x^2)^5(1 + x^2 + x^4)^3(1 + x^4)). [See column t6,m in table 1 p. 12 of Guttmann and Conway.]

Crossrefs

Sequence in context: A069039 A156196 A041270 * A346446 A064121 A064116

Adjacent sequences: A055909 A055910 A055911 * A055913 A055914 A055915

Keyword

nonn

Author

Christian G. Bower, Jun 22 2000

Status

approved