G.f. A(x) satisfies A(x) = 1 + x*A(x)^4*A(-x).

Terms

a(0) =1a(1) =1a(2) =3a(3) =17a(4) =85a(5) =598a(6) =3473a(7) =26668a(8) =166429a(9) =1340079a(10) =8724438a(11) =72374714a(12) =484498327a(13) =4102336176a(14) =28009706440a(15) =240729330116