G.f. A(x) satisfies: A(x) = x + x^2 + x^3 * (1 + A(A(x))).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =4a(6) =8a(7) =18a(8) =45a(9) =122a(10) =350a(11) =1052a(12) =3313a(13) =10933a(14) =37739a(15) =135865a(16) =508545a(17) =1973717a(18) =7926795a(19) =32895354a(20) =140894024a(21) =622160220a(22) =2829323210a(23) =13235526027a(24) =63620528705a(25) =313909404040