Solution (source code)

= Solution

For a positively oriented circle of any radius $R>0$, the <residue theorem> gives
$$
\boxed{\oint_{|z|=R}f(z)\,dz=2\pi i\frac{n^{n+1}}{(n+1)!}.}
$$
Only the $z^{-1}$ coefficient in the <Laurent series> contributes. Reversing the <orientation> changes the sign.