Sum of squares of natural numbers and geometric series

Question

Sn = 0.4^0 + 1^2.4^1 + 2^2.4^2 + 3^2.4^3 + ...... + n^2.4^n

ie- Sn = Sum(i^2.4^i)

I need help with this problem. I integrated it using ILATE rule and found the le