G.f. satisfies: A(x) = (1 + x*A(x))*(1 + x^2*A(x)^4).

Terms

a(0) =1a(1) =1a(2) =2a(3) =7a(4) =26a(5) =102a(6) =424a(7) =1827a(8) =8078a(9) =36466a(10) =167376a(11) =778718a(12) =3664164a(13) =17407068a(14) =83375616a(15) =402198915a(16) =1952296598a(17) =9528757098a(18) =46735576816a(19) =230227356906