\[ \boxed { \left ( {x}^{2}-1 \right ) {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) +2\,x{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) -ly \left ( x \right ) =0} \]
Mathematica: cpu = 0.014002 (sec), leaf count = 46 \[ \left \{\left \{y(x)\to c_1 P_{\frac {1}{2} \left (\sqrt {4 l+1}-1\right )}(x)+c_2 Q_{\frac {1}{2} \left (\sqrt {4 l+1}-1\right )}(x)\right \}\right \} \]
Maple: cpu = 0.031 (sec), leaf count = 35 \[ \left \{ y \left ( x \right ) ={\it \_C1}\,{\it LegendreP} \left ( { \frac {1}{2}\sqrt {1+4\,l}}-{\frac {1}{2}},x \right ) +{\it \_C2}\,{ \it LegendreQ} \left ( {\frac {1}{2}\sqrt {1+4\,l}}-{\frac {1}{2}},x \right ) \right \} \]