Expansion of e.g.f. (1 + x * exp(x))^4.

Terms

a(0) =1a(1) =4a(2) =20a(3) =108a(4) =616a(5) =3620a(6) =21624a(7) =129892a(8) =778208a(9) =4621572a(10) =27080680a(11) =156080804a(12) =883304976a(13) =4905620356a(14) =26743018904a(15) =143219056740a(16) =754280089024