\[ a y(x) y''(x)+y^{(3)}(x)=0 \] ✗ Mathematica : cpu = 0.037189 (sec), leaf count = 0 , could not solve
DSolve[a*y[x]*Derivative[2][y][x] + Derivative[3][y][x] == 0, y[x], x]
✓ Maple : cpu = 1.15 (sec), leaf count = 129
\[\left \{y \left (x \right ) = \mathit {ODESolStruc} \left ({\mathrm e}^{c_{2}+\int \textit {\_g} \left (\textit {\_f} \right )d \textit {\_f}}, \left [\left \{\frac {d}{d \textit {\_f}}\textit {\_g} \left (\textit {\_f} \right )=\frac {\left (6 \textit {\_f}^{2} \textit {\_g} \left (\textit {\_f} \right )^{2}+2 \textit {\_f} a \textit {\_g} \left (\textit {\_f} \right )^{2}+7 \textit {\_f} \textit {\_g} \left (\textit {\_f} \right )+a \textit {\_g} \left (\textit {\_f} \right )+1\right ) \textit {\_g} \left (\textit {\_f} \right )}{\textit {\_f}}\right \}, \left \{\textit {\_f} =\frac {\frac {d}{d x}y \left (x \right )}{y \left (x \right )^{2}}, \textit {\_g} \left (\textit {\_f} \right )=\frac {\left (\frac {d}{d x}y \left (x \right )\right ) y \left (x \right )^{2}}{\left (\frac {d^{2}}{d x^{2}}y \left (x \right )\right ) y \left (x \right )-2 \left (\frac {d}{d x}y \left (x \right )\right )^{2}}\right \}, \left \{x =c_{1}+\int \frac {\textit {\_g} \left (\textit {\_f} \right ) {\mathrm e}^{-c_{2}+\int -\textit {\_g} \left (\textit {\_f} \right )d \textit {\_f}}}{\textit {\_f}}d \textit {\_f} , y \left (x \right )={\mathrm e}^{c_{2}+\int \textit {\_g} \left (\textit {\_f} \right )d \textit {\_f}}\right \}\right ]\right )\right \}\]