I'm trying to figure out the generating function for this power series.. I have a few ideas but can't get any result..
$\sum_{n=2}^\infty \left(\sum_{k=1}^{n} ((n-k)(k-1)M_{k-1}) z^n\right) $
$M(k)$ is my recursive function.. my problem is with the $(n-k)(k-1)$ part..
I was thinking that it can be extracted from the summation and it should become
$n(n+1)(n+2)/6$
but I'm still unable to solve this..