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

Terms

a(0) =1a(1) =1a(2) =4a(3) =15a(4) =70a(5) =360a(6) =1953a(7) =11008a(8) =63837a(9) =378390a(10) =2282205a(11) =13960890a(12) =86411232a(13) =540166219a(14) =3405341160a(15) =21625820793a(16) =138216775785a(17) =888371346825