G.f. A(x) satisfies: A(x) = Sum_{n>=0} x^n * (1+x)^(n^2) / A(x)^(n*(n+1)/2).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =2a(7) =5a(8) =18a(9) =61a(10) =229a(11) =879a(12) =3588a(13) =15283a(14) =68029a(15) =314985a(16) =1512982a(17) =7523664a(18) =38653397a(19) =204844184a(20) =1118152388a(21) =6278617770a(22) =36225373016a(23) =214531854676