G.f. satisfies A(x) = x + Sum_{n>=1} A(x^n)^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =16a(5) =51a(6) =158a(7) =524a(8) =1762a(9) =6089a(10) =21326a(11) =75879a(12) =272794a(13) =990673a(14) =3626536a(15) =13371544a(16) =49606460a(17) =185046037a(18) =693621174a(19) =2611275523a(20) =9869097706a(21) =37431498607a(22) =142426706634a(23) =543524937780