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

Author

Christian G. Bower, Jun 13 2000

Keywords

• nonn

Links

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

Crossrefs

Cf. A055898.

Formula

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