\[ \boxed { x{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) -x{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) -ay \left ( x \right ) =0} \]
Mathematica: cpu = 0.040505 (sec), leaf count = 36 \[ \left \{\left \{y(x)\to c_2 G_{1,2}^{2,0}\left (-x\left | \begin {array}{c} 1-a \\ 0,1 \\ \end {array} \right .\right )+c_1 x \, _1F_1(a+1;2;x)\right \}\right \} \]
Maple: cpu = 0.094 (sec), leaf count = 23 \[ \left \{ y \left ( x \right ) ={\it \_C1}\,x{{\sl M}\left (a+1,\,2,\,x \right )}+{\it \_C2}\,x{{\sl U}\left (a+1,\,2,\,x\right )} \right \} \]