G.f. A(x) satisfies: A(x)^3 - 3*A(x)^4 = A(x^3).

Terms

a(0) =1a(1) =1a(2) =3a(3) =12a(4) =52a(5) =246a(6) =1224a(7) =6300a(8) =33300a(9) =179643a(10) =985014a(11) =5473611a(12) =30756638a(13) =174460232a(14) =997620618a(15) =5744867987a(16) =33286011182a(17) =193909247415