\[ \boxed { {x}^{2}{\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left ( x \right ) +6\,x{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) +6\,{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +a{x}^{2}y \left ( x \right ) =0} \]
Mathematica: cpu = 0.273535 (sec), leaf count = 63 \[ \left \{\left \{y(x)\to \frac {c_1 e^{-\sqrt [3]{a} x}}{x^2}+\frac {c_2 e^{\sqrt [3]{-1} \sqrt [3]{a} x}}{x^2}+\frac {c_3 e^{-(-1)^{2/3} \sqrt [3]{a} x}}{x^2}\right \}\right \} \]
Maple: cpu = 0.031 (sec), leaf count = 67 \[ \left \{ y \left ( x \right ) ={\frac {1}{{x}^{2}} \left ( {\it \_C1}\,{ {\rm e}^{ \left ( -{\frac {1}{2}\sqrt [3]{-a}}+{\frac {i}{2}}\sqrt {3} \sqrt [3]{-a} \right ) x}}+{\it \_C2}\,{{\rm e}^{ \left ( -{\frac {1}{2} \sqrt [3]{-a}}-{\frac {i}{2}}\sqrt {3}\sqrt [3]{-a} \right ) x}}+{\it \_C3}\,{{\rm e}^{\sqrt [3]{-a}x}} \right ) } \right \} \]