\[ (-a-x) y(x)+x^2 y''(x)+x y'(x)=0 \] ✓ Mathematica : cpu = 0.0384322 (sec), leaf count = 78
\[\left \{\left \{y(x)\to (-1)^{-\sqrt {a}} c_1 \Gamma \left (1-2 \sqrt {a}\right ) I_{-2 \sqrt {a}}\left (2 \sqrt {x}\right )+(-1)^{\sqrt {a}} c_2 \Gamma \left (2 \sqrt {a}+1\right ) I_{2 \sqrt {a}}\left (2 \sqrt {x}\right )\right \}\right \}\] ✓ Maple : cpu = 0.013 (sec), leaf count = 31
\[\left \{y \left (x \right ) = c_{1} \BesselI \left (2 \sqrt {a}, 2 \sqrt {x}\right )+c_{2} \BesselK \left (2 \sqrt {a}, 2 \sqrt {x}\right )\right \}\]