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

Terms

a(0) =1a(1) =1a(2) =4a(3) =18a(4) =94a(5) =529a(6) =3135a(7) =19270a(8) =121732a(9) =785496a(10) =5155167a(11) =34304706a(12) =230923653a(13) =1569684910a(14) =10759159000a(15) =74281473504a(16) =516089542684