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A055900 Column 4 of triangle A055898. 0
1, 9, 51, 209, 696, 1980, 5000, 11475, 24375, 48545, 91581, 164934, 285376, 476784, 772416, 1217610, 1873125, 2819025, 4159375, 6027615, 8592936, 12067484, 16714776, 22859109, 30896411, 41306265, 54665625, 71663900 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,2

LINKS

Table of n, a(n) for n=4..31.

A. J. Guttmann, Indicators of solvability for lattice models, Discrete Math., 217 (2000), 167-189 (H_4 for square lattices of Section 6).

FORMULA

G.f.: x^4(1+3x+9x^2+9x^3+9x^4+3x^5+x^6)/((1-x)^9(1+x)^3).

CROSSREFS

Sequence in context: A034816 A140381 A282877 * A054549 A005746 A220236

Adjacent sequences:  A055897 A055898 A055899 * A055901 A055902 A055903

KEYWORD

nonn

AUTHOR

Christian G. Bower, Jun 13 2000

STATUS

approved

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Last modified July 20 22:54 EDT 2019. Contains 325189 sequences. (Running on oeis4.)