\[e^{-\frac{1}{2}y}\left(\frac{x}{x+y}\right)^{\mu-\frac{1}{2}}\sum_{n=0}^{%
\infty}\frac{{\left(\frac{1}{2}-\mu-\kappa\right)_{n}}}{n!}\left(\frac{-y}{%
\sqrt{x}}\right)^{n}\*W_{\kappa-\frac{1}{2}n,\mu-\frac{1}{2}n}\left(x\right),\]