G.f. A(x) satisfies: x^2*A(x) = Sum_{n=-oo..+oo} (-1)^n * x^(n*(n+1)/2) * A(x)^n.

Terms

a(0) =1a(1) =0a(2) =1a(3) =3a(4) =11a(5) =34a(6) =110a(7) =350a(8) =1147a(9) =3800a(10) =12836a(11) =43929a(12) =152285a(13) =533205a(14) =1883187a(15) =6698612a(16) =23974179a(17) =86258459a(18) =311811314a(19) =1131863444a(20) =4124127216a(21) =15078422405a(22) =55301519095a(23) =203405409935a(24) =750122683729