\[ (n+1) a^{2 n} y(x)^{2 n+1}+y''(x)-y(x)=0 \] ✗ Mathematica : cpu = 300.2 (sec), leaf count = 0 , timed out
$Aborted
✓ Maple : cpu = 0.244 (sec), leaf count = 73
\[ \left \{ \int ^{y \left ( x \right ) }\!{\frac {1}{\sqrt {-{a}^{2\,n}{{\it \_a}}^{2\,n+2}+{{\it \_a}}^{2}+{\it \_C1}}}}{d{\it \_a}}-x-{\it \_C2}=0,\int ^{y \left ( x \right ) }\!-{\frac {1}{\sqrt {-{a}^{2\,n}{{\it \_a}}^{2\,n+2}+{{\it \_a}}^{2}+{\it \_C1}}}}{d{\it \_a}}-x-{\it \_C2}=0 \right \} \]