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

Terms

a(0) =1a(1) =1a(2) =3a(3) =9a(4) =37a(5) =168a(6) =813a(7) =4088a(8) =21129a(9) =111540a(10) =598832a(11) =3259632a(12) =17948205a(13) =99791350a(14) =559473468a(15) =3159345810a(16) =17953664613a(17) =102594485202a(18) =589169987088