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A055908 Column 2 of triangle A055907. 1
1, 4, 10, 21, 39, 67, 107, 163, 238, 337, 463, 622, 818, 1058, 1346, 1690, 2095, 2570, 3120, 3755, 4481, 5309, 6245, 7301, 8484, 9807, 11277, 12908, 14708, 16692, 18868, 21252, 23853, 26688, 29766, 33105, 36715, 40615, 44815, 49335, 54186 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Table of n, a(n) for n=2..42.

A. J. Guttmann, Indicators of solvability for lattice models, Discrete Math., 217 (2000), 167-189 (H_2 for hexagonal lattices of Section 6).

FORMULA

G.f.: x^2(1 + x + x^3)/((1 - x)^5(1+x)^2(1 + x^2)).

CROSSREFS

Sequence in context: A253688 A049480 A216172 * A023538 A085360 A265050

Adjacent sequences:  A055905 A055906 A055907 * A055909 A055910 A055911

KEYWORD

nonn

AUTHOR

Christian G. Bower, Jun 14 2000

STATUS

approved

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Last modified February 19 16:56 EST 2018. Contains 299356 sequences. (Running on oeis4.)