4,2

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

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

Sequence in context: A034816 A140381 A140389 this_sequence A054549 A005746 A061178

Adjacent sequences: A055897 A055898 A055899 this_sequence A055901 A055902 A055903

nonn

Christian G. Bower (bowerc(AT)usa.net), Jun 13 2000