OFFSET
1,2
LINKS
M. F. Sykes and M. E. Fisher, Antiferromagnetic susceptibility of the plane square and honeycomb Ising lattices, Physica, 28 (1962), 919-938.
FORMULA
G.f.: (2*(1-y^2)*u(y^2) + 4*((2-y)^2*xi(y^2)-1)) / (1+y)^2, where u(x) is the g.f. of A002909 and xi(x) is the g.f. of A002979. - Andrey Zabolotskiy, Mar 03 2021
CROSSREFS
KEYWORD
sign,more
AUTHOR
STATUS
approved