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

Terms

a(0) =1a(1) =1a(2) =3a(3) =12a(4) =56a(5) =279a(6) =1464a(7) =7972a(8) =44631a(9) =255279a(10) =1485309a(11) =8763474a(12) =52308615a(13) =315300734a(14) =1916541654a(15) =11734469820a(16) =72304205945a(17) =448014505908