\[ -a x^2 y(x)+x y^{(3)}(x)+3 y''(x)=0 \] ✓ Mathematica : cpu = 0.0445613 (sec), leaf count = 104
\[\left \{\left \{y(x)\to -\frac {2 (-1)^{3/4} \sqrt {2} c_1 \, _0F_2\left (;\frac {1}{2},\frac {3}{4};\frac {a x^4}{64}\right )}{\sqrt [4]{a} x}+c_2 \, _0F_2\left (;\frac {3}{4},\frac {5}{4};\frac {a x^4}{64}\right )+\frac {\sqrt [4]{-1} \sqrt [4]{a} c_3 x \, _0F_2\left (;\frac {5}{4},\frac {3}{2};\frac {a x^4}{64}\right )}{2 \sqrt {2}}\right \}\right \}\] ✓ Maple : cpu = 0.102 (sec), leaf count = 48
\[\left \{y \left (x \right ) = c_{3} x \hypergeom \left (\left [\right ], \left [\frac {5}{4}, \frac {3}{2}\right ], \frac {a \,x^{4}}{64}\right )+c_{1} \hypergeom \left (\left [\right ], \left [\frac {3}{4}, \frac {5}{4}\right ], \frac {a \,x^{4}}{64}\right )+\frac {c_{2} \hypergeom \left (\left [\right ], \left [\frac {1}{2}, \frac {3}{4}\right ], \frac {a \,x^{4}}{64}\right )}{x}\right \}\]