While searching for a summation formula I come accross the following equation on wikipedia Equation $$\sum\limits_{k=1}^{n}{k^m z^k}=\left(z\frac{d}{dz}\right)^m\frac{z-z^{n+1}}{1-z}$$
So I tried to simplify it but it is getting complex and I am unable to come up with any sort form this summation equation. Please help me
Thanks in advance.