By integration, differentiation, or any other valid operation : I am asked to find the function which these represent

$$\sum\_1^\infty n^2x^n$$

I tried doing everything - but I just can't do it. What I've done so far :

The series is convergent $<=>$ $-1<x<1$
And uniformly convergent on a compact set $K \subset (-1,1)$ So I can use the property of uniformly convergent series to use differentiation integration etc. But I couldn't move a pencil. Any help will be appreciated