Expansion of e.g.f.: 1 + x*exp(x) + x^2*exp(2*x) + x^3*exp(3*x).

Terms

a(0) =1a(1) =1a(2) =4a(3) =21a(4) =124a(5) =705a(6) =3726a(7) =18361a(8) =85240a(9) =376641a(10) =1597690a(11) =6551721a(12) =26116740a(13) =101647585a(14) =387634534a(15) =1452554265a(16) =5360857456a(17) =19523426433a(18) =70272302706a(19) =250318462537a(20) =883418329660