0,3

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

G.f.: H_2(x) = x*(1 + x + x^2)/((1 - x)^5*(1+x))

Sequence in context: A131283 A082199 A082190 this_sequence A027085 A099452 A006007

Adjacent sequences: A011860 A011861 A011862 this_sequence A011864 A011865 A011866

nonn

R. K. Guy