G.f. satisfies A(x) = (1 + x*A(x))^2 * (1 + x^2*A(x)^3).

Terms

a(0) =1a(1) =2a(2) =6a(3) =24a(4) =111a(5) =552a(6) =2873a(7) =15458a(8) =85312a(9) =480314a(10) =2747845a(11) =15928080a(12) =93347153a(13) =552181372a(14) =3292571913a(15) =19769887128a(16) =119430685503a(17) =725375643416