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

Terms

a(0) =1a(1) =0a(2) =0a(3) =1a(4) =1a(5) =0a(6) =3a(7) =6a(8) =3a(9) =12a(10) =36a(11) =36a(12) =67a(13) =220a(14) =330a(15) =493a(16) =1420a(17) =2730a(18) =4158a(19) =9933a(20) =21693a(21) =36312a(22) =75684a(23) =171360a(24) =316011a(25) =617424a(26) =1374156a(27) =2723667a(28) =5256237a(29) =11303028