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

Terms

a(0) =1a(1) =1a(2) =3a(3) =10a(4) =37a(5) =147a(6) =611a(7) =2625a(8) =11564a(9) =51953a(10) =237123a(11) =1096420a(12) =5125063a(13) =24178427a(14) =114974387a(15) =550511901a(16) =2651896733a(17) =12843003108a(18) =62494595022a(19) =305400429548