a(n) = (n^3 - n)*5^n.

Terms

a(0) =0a(1) =150a(2) =3000a(3) =37500a(4) =375000a(5) =3281250a(6) =26250000a(7) =196875000a(8) =1406250000a(9) =9667968750a(10) =64453125000a(11) =418945312500