\[ \boxed { {x}^{2}{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) +x{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) -y \left ( x \right ) -a{x}^{2}=0} \]
Mathematica: cpu = 0.014502 (sec), leaf count = 44 \[ \left \{\left \{y(x)\to \frac {a x^2}{3}+\frac {c_1 \left (x^2+1\right )}{2 x}+\frac {i c_2 \left (x^2-1\right )}{2 x}\right \}\right \} \]
Maple: cpu = 0.016 (sec), leaf count = 19 \[ \left \{ y \left ( x \right ) =x{\it \_C2}+{\frac {a{x}^{2}}{3}}+{\frac {{\it \_C1}}{x}} \right \} \]