\[ \boxed { 16\,x{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) +8\,{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) - \left ( x+a \right ) y \left ( x \right ) =0} \]
Mathematica: cpu = 0.012502 (sec), leaf count = 74 \[ \left \{\left \{y(x)\to c_1 e^{\frac {1}{4} (2 \log (x)-x)} U\left (\frac {a+6}{8},\frac {3}{2},\frac {x}{2}\right )+c_2 e^{\frac {1}{4} (2 \log (x)-x)} L_{\frac {1}{8} (-a-6)}^{\frac {1}{2}}\left (\frac {x}{2}\right )\right \}\right \} \]
Maple: cpu = 0.063 (sec), leaf count = 43 \[ \left \{ y \left ( x \right ) ={\it \_C1}\,\sqrt {x}{{\rm e}^{-{\frac {x }{4}}}}{{\sl M}\left ({\frac {a}{8}}+{\frac {3}{4}},\,{\frac {3}{2}},\, {\frac {x}{2}}\right )}+{\it \_C2}\,\sqrt {x}{{\rm e}^{-{\frac {x}{4}}} }{{\sl U}\left ({\frac {a}{8}}+{\frac {3}{4}},\,{\frac {3}{2}},\,{ \frac {x}{2}}\right )} \right \} \]