\[K_{n}\left(z\right)=\frac{n!(\tfrac{1}{2}z)^{-n}}{2}\sum_{k=0}^{n-1}(-1)^{k}%
\frac{(\tfrac{1}{2}z)^{k}I_{k}\left(z\right)}{k!(n-k)}+(-1)^{n-1}\left(\ln%
\left(\tfrac{1}{2}z\right)-\psi\left(n+1\right)\right)I_{n}\left(z\right)+(-1)%
^{n}\sum_{k=1}^{\infty}\frac{(n+2k)I_{n+2k}\left(z\right)}{k(n+k)},\]