Would really appreciate help on the following problem. I'm given the pdf of a discrete random variable R given by

P(R=j) = (j+1)*(1-p)^(2)*p^(j) j=0,1,2,.... and 0<p<1.

I have to show that the probability generating function of R is:

G(s)= [(1-p)/(1-ps)]^2

Apologies for the way I've written it, just tried to use LaTeX but I couldn't get it right.

Thank you in advance.