a(n) = n*5^n.

Terms

a(0) =0a(1) =5a(2) =50a(3) =375a(4) =2500a(5) =15625a(6) =93750a(7) =546875a(8) =3125000a(9) =17578125a(10) =97656250a(11) =537109375a(12) =2929687500a(13) =15869140625a(14) =85449218750a(15) =457763671875