\[ y'(x)-a x^n \left (y(x)^2+1\right )=0 \] ✓ Mathematica : cpu = 0.0298574 (sec), leaf count = 21
\[\left \{\left \{y(x)\to \tan \left (\frac {a x^{n+1}}{n+1}+c_1\right )\right \}\right \}\]
✓ Maple : cpu = 0.04 (sec), leaf count = 26
\[ \left \{ y \left ( x \right ) =\tan \left ( {\frac {{\it \_C1}\,an+{x}^{n+1}a+{\it \_C1}\,a}{n+1}} \right ) \right \} \]