\[ \boxed { {x}^{2}{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) -x{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +y \left ( x \right ) -3\,{x}^{3}=0} \]
Mathematica: cpu = 0.012502 (sec), leaf count = 23 \[ \left \{\left \{y(x)\to c_1 x+c_2 x \log (x)+\frac {3 x^3}{4}\right \}\right \} \]
Maple: cpu = 0.015 (sec), leaf count = 18 \[ \left \{ y \left ( x \right ) =x{\it \_C2}+x\ln \left ( x \right ) {\it \_C1}+{\frac {3\,{x}^{3}}{4}} \right \} \]