>>235
E[exp(nt)] = Σ_{n=0 to ∞} (k+n-1, n) * p^k * {(1-p)*exp(t)}^n
= (p^k) Σ (k+n-1, n) * {(1-p)*exp(t)}^n
= (p^k) { 1/(1-(1-p)*exp(t))}^k