\[ \boxed { {\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left ( x \right ) +x{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +ny \left ( x \right ) =0} \]
Mathematica: cpu = 0.018502 (sec), leaf count = 103 \[ \left \{\left \{y(x)\to \frac {c_2 x \, _1F_2\left (\frac {n}{3}+\frac {1}{3};\frac {2}{3},\frac {4}{3};-\frac {x^3}{9}\right )}{3^{2/3}}+c_1 \, _1F_2\left (\frac {n}{3};\frac {1}{3},\frac {2}{3};-\frac {x^3}{9}\right )+\frac {c_3 x^2 \, _1F_2\left (\frac {n}{3}+\frac {2}{3};\frac {4}{3},\frac {5}{3};-\frac {x^3}{9}\right )}{3 \sqrt [3]{3}}\right \}\right \} \]
Maple: cpu = 0.078 (sec), leaf count = 58 \[ \left \{ y \left ( x \right ) ={\it \_C1}\, {\mbox {$_1$F$_2$}({\frac {n}{3}};\,{\frac {1}{3}},{\frac {2}{3}};\,-{\frac {{x}^{3}}{9}})} +{\it \_C2}\,x {\mbox {$_1$F$_2$}({\frac {1}{3}}+{\frac {n}{3}};\,{\frac {2}{3}},{\frac {4}{3}};\,-{\frac {{x}^{3}}{9}})} +{\it \_C3}\,{x}^{2} {\mbox {$_1$F$_2$}({\frac {2}{3}}+{\frac {n}{3}};\,{\frac {4}{3}},{\frac {5}{3}};\,-{\frac {{x}^{3}}{9}})} \right \} \]