\[ \left (4 x^2-1\right ) y(x)+y''(x)-4 x y'(x)-e^x=0 \] ✓ Mathematica : cpu = 0.0597842 (sec), leaf count = 109
\[\left \{\left \{y(x)\to \frac {1}{4} \sqrt {\pi } e^{x (x-i)-\frac {i}{2}} \left (e^{2 i x} \text {erfi}\left (\left (\frac {1}{2}+\frac {i}{2}\right )-i x\right )-i e^i \text {erf}\left (-x+\left (\frac {1}{2}+\frac {i}{2}\right )\right )\right )+c_1 e^{x (x-i)}-\frac {1}{2} i c_2 e^{(x-i) x+2 i x}\right \}\right \}\] ✓ Maple : cpu = 0.182 (sec), leaf count = 66
\[\left \{y \left (x \right ) = \frac {\left (4 c_{1} \sin \left (x \right )+4 c_{2} \cos \left (x \right )+\left (i \cos \left (x \right )+\sin \left (x \right )\right ) {\mathrm e}^{\frac {i}{2}} \sqrt {\pi }\, \erf \left (x -\frac {1}{2}-\frac {i}{2}\right )-\left (i \cos \left (x \right )-\sin \left (x \right )\right ) {\mathrm e}^{-\frac {i}{2}} \sqrt {\pi }\, \erf \left (x -\frac {1}{2}+\frac {i}{2}\right )\right ) {\mathrm e}^{x^{2}}}{4}\right \}\]