A055900 Column 4 of triangle A055898.

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

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

Cf. A055898.

Sequence in context: A140381 A330805 A282877 * A054549 A005746 A220236

Adjacent sequences: A055897 A055898 A055899 * A055901 A055902 A055903

Keyword

nonn

Author

Christian G. Bower, Jun 13 2000

Status

approved