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

Terms

a(0) =1a(1) =1a(2) =3a(3) =12a(4) =56a(5) =285a(6) =1533a(7) =8571a(8) =49311a(9) =290019a(10) =1735845a(11) =10538550a(12) =64741482a(13) =401708635a(14) =2513837901a(15) =15847466748a(16) =100547969532a(17) =641570954283