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

Terms

a(0) =1a(1) =1a(2) =3a(3) =11a(4) =44a(5) =193a(6) =882a(7) =4178a(8) =20305a(9) =100694a(10) =507493a(11) =2591897a(12) =13384911a(13) =69773480a(14) =366661360a(15) =1940336952a(16) =10331179153a(17) =55306072496a(18) =297499878304