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

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =48a(6) =163a(7) =573a(8) =2074a(9) =7669a(10) =28860a(11) =110148a(12) =425384a(13) =1659185a(14) =6526791a(15) =25863949a(16) =103151955a(17) =413728474a(18) =1667757766a(19) =6753022725a(20) =27454555171a(21) =112024545382a(22) =458616153319