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

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =20a(5) =72a(6) =272a(7) =1065a(8) =4282a(9) =17576a(10) =73344a(11) =310226a(12) =1327036a(13) =5730948a(14) =24952776a(15) =109417672a(16) =482779032a(17) =2141832444a(18) =9548501992a(19) =42753897498a(20) =192184437012a(21) =866963862560