G.f. A(x) satisfies A(x)^3 = A( x*A(x)^2*(1 + A(x))^2 ).

Terms

a(0) =1a(1) =2a(2) =5a(3) =16a(4) =62a(5) =264a(6) =1170a(7) =5310a(8) =24599a(9) =116092a(10) =556613a(11) =2703650a(12) =13274152a(13) =65764358a(14) =328361751a(15) =1650666672a(16) =8347486950a(17) =42437045604a(18) =216759551139