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

Terms

a(0) =1a(1) =2a(2) =4a(3) =14a(4) =52a(5) =204a(6) =840a(7) =3586a(8) =15708a(9) =70196a(10) =318792a(11) =1467068a(12) =6826360a(13) =32062184a(14) =151805328a(15) =723785606a(16) =3472055348a(17) =16745865716a(18) =81154862712a(19) =394993248572