\[ \left (1-a^2\right ) x y'(x)+x^3 y^{(3)}(x)+3 x^2 y''(x)=0 \] ✓ Mathematica : cpu = 0.0328694 (sec), leaf count = 29
\[\left \{\left \{y(x)\to -\frac {c_1 x^{-a}}{a}+\frac {c_2 x^a}{a}+c_3\right \}\right \}\] ✓ Maple : cpu = 0.009 (sec), leaf count = 18
\[ \left \{ y \left ( x \right ) ={\it \_C1}+{x}^{a}{\it \_C2}+{\it \_C3}\,{x}^{-a} \right \} \]