Expansion of e.g.f. x^3/(1-3*x).

Terms

a(0) =0a(1) =0a(2) =0a(3) =6a(4) =72a(5) =1080a(6) =19440a(7) =408240a(8) =9797760a(9) =264539520a(10) =7936185600a(11) =261894124800