\[ \boxed { x{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) + \left ( ax+b+n \right ) {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +nay \left ( x \right ) =0} \]
Mathematica: cpu = 0.053507 (sec), leaf count = 43 \[ \left \{\left \{y(x)\to c_1 e^{-a x} U(b,b+n,a x)+c_2 e^{-a x} L_{-b}^{b+n-1}(a x)\right \}\right \} \]
Maple: cpu = 0.078 (sec), leaf count = 35 \[ \left \{ y \left ( x \right ) ={\it \_C1}\,{{\rm e}^{-ax}}{{\sl M}\left ( b,\,b+n,\,ax\right )}+{\it \_C2}\,{{\rm e}^{-ax}}{{\sl U}\left (b,\,b+n ,\,ax\right )} \right \} \]