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

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =5a(5) =12a(6) =30a(7) =80a(8) =221a(9) =624a(10) =1798a(11) =5271a(12) =15662a(13) =47052a(14) =142686a(15) =436187a(16) =1342669a(17) =4158048a(18) =12945758a(19) =40497415a(20) =127225426a(21) =401222453a(22) =1269712425a(23) =4030877287a(24) =12833659158a(25) =40968993548a(26) =131106215470a(27) =420507819784