Expansion of e.g.f. exp(x * (1+x)^3).

Terms

a(0) =1a(1) =1a(2) =7a(3) =37a(4) =241a(5) =1981a(6) =17551a(7) =171697a(8) =1860097a(9) =21609721a(10) =268697431a(11) =3566446621a(12) =50060084977a(13) =740156116597