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

Terms

a(0) =1a(1) =1a(2) =4a(3) =19a(4) =101a(5) =578a(6) =3479a(7) =21714a(8) =139269a(9) =912354a(10) =6078832a(11) =41066002a(12) =280636657a(13) =1936569717a(14) =13475408847a(15) =94446518559a(16) =666149216744