Expansion of e.g.f. 5*x/(1-x).

Terms

a(0) =0a(1) =5a(2) =10a(3) =30a(4) =120a(5) =600a(6) =3600a(7) =25200a(8) =201600a(9) =1814400a(10) =18144000a(11) =199584000a(12) =2395008000a(13) =31135104000a(14) =435891456000