Lommel function
The Lommel differential equation, named after Eugen von Lommel, is an inhomogeneous form of the Bessel differential equation: z 2 d 2 y d z 2 + z d y d z + ( z 2 − ν 2 ) y = z μ + 1 . {\displaystyle z^{2}{\frac {d^{2}y}{dz^{2}}}+z{\frac {dy}{dz}}+(z^{2}-\nu ^{2})y=z^{\mu +1}.} Solutions are given by the Lommel functions sμ,ν(z) and Sμ,ν(z), introduced by Eugen von Lommel (1880), s μ , ν ( z ) = π 2 [ Y ν ( z ) ∫ 0 z x μ J ν ( x ) d x − J ν ( z ) ∫ 0 z x μ Y ν ( x ) d x ] , {\displaystyle s_{\mu ,\nu }(z)={\frac {\pi }{2}}\left[Y_{\nu }(z)\! \int _{0}^{z}\!