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

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =18a(5) =49a(6) =135a(7) =383a(8) =1104a(9) =3228a(10) =9554a(11) =28557a(12) =86095a(13) =261487a(14) =799323a(15) =2457327a(16) =7592620a(17) =23565444a(18) =73437284a(19) =229691620a(20) =720800824a(21) =2268820824a(22) =7161255962a(23) =22661307317a(24) =71878917199a(25) =228487568175a(26) =727779875401