Laurent Series Expansion for Cotangent Function

Corollary to Laurent Series Expansion for Cotangent Function

 * $\displaystyle \pi \cot \pi z = \frac 1 z - 2\sum_{n=1}^\infty \zeta\left(2n\right)z^{2n-1}$

For $|z| < 1$, where $\zeta$ is the Riemann Zeta function.