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

Terms

a(0) =1a(1) =0a(2) =0a(3) =1a(4) =3a(5) =3a(6) =3a(7) =12a(8) =30a(9) =45a(10) =75a(11) =192a(12) =436a(13) =798a(14) =1554a(15) =3542a(16) =7740a(17) =15543a(18) =32183a(19) =70794a(20) =153252a(21) =321431a(22) =684123a(23) =1491504a(24) =3232672a(25) =6928779a(26) =14957787a(27) =32615388a(28) =70991040a(29) =153985890