\[K_{n}\left(z\right)=\frac{(-1)^{n-1}}{2}\*\left(\left.\frac{\partial I_{\nu}%
\left(z\right)}{\partial\nu}\right|_{\nu=n}+\left.\frac{\partial I_{\nu}\left(%
z\right)}{\partial\nu}\right|_{\nu=-n}\right),\]