$$f\left(x;\nu ,\lambda \right)=\sum _{i=0}^{\infty }\frac{e^{\left(-\frac{\lambda }{2}\right)}{\left(\frac{\lambda }{2}\right)}^i}{i!}f\left(x;\nu +2i\right)=\frac{1}{2}{e}^{[-\frac{\left(x+\lambda \right)}{2}]}{\left(\frac{x}{\lambda }\right)}^{\left(\frac{\nu }{4}-\frac{1}{2}\right)}{I}_{\left(\frac{k}{2}-1\right)}\left(\sqrt{\lambda x}\right)$$