\[ y''(x)-e^{y(x)}=0 \] ✓ Mathematica : cpu = 0.0400051 (sec), leaf count = 34
\[\left \{\left \{y(x)\to \log \left (\frac {1}{2} c_1 \left (-1+\tanh ^2\left (\frac {1}{2} \sqrt {c_1 (x+c_2){}^2}\right )\right )\right )\right \}\right \}\] ✓ Maple : cpu = 1.542 (sec), leaf count = 23
\[ \left \{ y \left ( x \right ) =\ln \left ( {\frac {1}{2\,{{\it \_C1}}^{2}} \left ( \left ( \tan \left ( {\frac {{\it \_C2}+x}{2\,{\it \_C1}}} \right ) \right ) ^{2}+1 \right ) } \right ) \right \} \]