Sum of Sequence of n by 2 to the Power of n/Proof 2

Proof
From Sum of Sequence of Power by Index:


 * $\displaystyle \sum_{j \mathop = 0}^n j x^j = \frac {n x^{n + 2} - \left({n + 1}\right) x^{n + 1} + x} {\left({x - 1}\right)^2}$

Hence:

Hence the result.