\[
\boxed{
2\, \left( x-{\it a1} \right)  \left( x-{\it a2} \right)  \left( x-{\it a3} \right) {\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left( x \right) + \left( 9\,{x}^{2}-6\, \left( {\it a1}+{\it a2}+{\it a3} \right) x+3\,{\it a1}\,{\it a2}+3\,{\it a1}\,{\it a3}+3\,{\it a2}\,{\it a3} \right) {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) -2\, \left(  \left( {n}^{2}+n-3 \right) x+b \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) -n \left( n+1 \right) y \left( x \right) =0}
\]