Modified Bessel differential equation ($z^2{w}^{\prime \prime }+z{w}^{\prime }-(z^2+{\nu }^2)w=0$)

The differential equation defining modified Bessel functions of order $\nu$. For real fixed $\nu$ and positive $z$, its independent standard solutions are $I_{\nu }(z)$ and $K_{\nu }(z)$.