\[ -y'(x) y''(x)+y(x)^3 y'(x)+y^{(3)}(x) y(x)=0 \] ✓ Mathematica : cpu = 2.00802 (sec), leaf count = 409
\[\left \{\left \{y(x)\to \text {InverseFunction}\left [-\frac {2 i \sqrt {1+\frac {\text {$\#$1}^2}{2 \left (\sqrt {c_2{}^2-c_1}-c_2\right )}} \sqrt {1-\frac {\text {$\#$1}^2}{2 \left (c_2+\sqrt {c_2{}^2-c_1}\right )}} F\left (i \sinh ^{-1}\left (\frac {\sqrt {\frac {1}{\sqrt {c_2{}^2-c_1}-c_2}} \text {$\#$1}}{\sqrt {2}}\right )|\frac {c_2-\sqrt {c_2{}^2-c_1}}{c_2+\sqrt {c_2{}^2-c_1}}\right )}{\sqrt {\frac {1}{\sqrt {c_2{}^2-c_1}-c_2}} \sqrt {-\frac {\text {$\#$1}^4}{2}+2 \text {$\#$1}^2 c_2-2 c_1}}\& \right ][x+c_3]\right \},\left \{y(x)\to \text {InverseFunction}\left [\frac {2 i \sqrt {1+\frac {\text {$\#$1}^2}{2 \left (\sqrt {c_2{}^2-c_1}-c_2\right )}} \sqrt {1-\frac {\text {$\#$1}^2}{2 \left (c_2+\sqrt {c_2{}^2-c_1}\right )}} F\left (i \sinh ^{-1}\left (\frac {\sqrt {\frac {1}{\sqrt {c_2{}^2-c_1}-c_2}} \text {$\#$1}}{\sqrt {2}}\right )|\frac {c_2-\sqrt {c_2{}^2-c_1}}{c_2+\sqrt {c_2{}^2-c_1}}\right )}{\sqrt {\frac {1}{\sqrt {c_2{}^2-c_1}-c_2}} \sqrt {-\frac {\text {$\#$1}^4}{2}+2 \text {$\#$1}^2 c_2-2 c_1}}\& \right ][x+c_3]\right \}\right \}\] ✓ Maple : cpu = 0.596 (sec), leaf count = 77
\[ \left \{ \int ^{y \left ( x \right ) }\!-2\,{\frac {1}{\sqrt {-{{\it \_a}}^{4}+4\,{\it \_C2}\,{{\it \_a}}^{2}-4\,{{\it \_C2}}^{2}+4\,{\it \_C1}}}}{d{\it \_a}}-x-{\it \_C3}=0,\int ^{y \left ( x \right ) }\!2\,{\frac {1}{\sqrt {-{{\it \_a}}^{4}+4\,{\it \_C2}\,{{\it \_a}}^{2}-4\,{{\it \_C2}}^{2}+4\,{\it \_C1}}}}{d{\it \_a}}-x-{\it \_C3}=0 \right \} \]