\[
\boxed{
x{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) -2\, \left( {x}^{2}-a \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) +2\,nxy \left( x \right) =0}
\]