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

Terms

a(0) =1a(1) =2a(2) =4a(3) =18a(4) =76a(5) =420a(6) =2248a(7) =14410a(8) =89676a(9) =642764a(10) =4487896a(11) =35282228a(12) =271094936a(13) =2310824808a(14) =19309255952a(15) =177093587874