a(1)=1, a(n) = n*5^(n-1) + a(n-1).

Terms

a(0) =1a(1) =11a(2) =86a(3) =586a(4) =3711a(5) =22461a(6) =131836a(7) =756836a(8) =4272461a(9) =23803711a(10) =131225586a(11) =717163086a(12) =3890991211a(13) =20980834961a(14) =112533569336a(15) =600814819336