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

Terms

a(0) =1a(1) =1a(2) =3a(3) =13a(4) =58a(5) =288a(6) =1512a(7) =8250a(8) =46296a(9) =265491a(10) =1548976a(11) =9165156a(12) =54865737a(13) =331694167a(14) =2022232068a(15) =12419023617a(16) =76755164643a(17) =477049187268