\[ x^{10} y^{(5)}(x)-a y(x)=0 \] ✓ Mathematica : cpu = 9.39229 (sec), leaf count = 114
DSolve[-(a*y[x]) + x^10*Derivative[5][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to c_1 x^4 e^{-\frac {\sqrt [5]{a}}{x}}+c_2 x^4 e^{\frac {\sqrt [5]{-1} \sqrt [5]{a}}{x}}+c_3 x^4 e^{-\frac {(-1)^{2/5} \sqrt [5]{a}}{x}}+c_4 x^4 e^{\frac {(-1)^{3/5} \sqrt [5]{a}}{x}}+c_5 x^4 e^{-\frac {(-1)^{4/5} \sqrt [5]{a}}{x}}\right \}\right \}\] ✓ Maple : cpu = 0.147 (sec), leaf count = 90
dsolve(x^10*diff(diff(diff(diff(diff(y(x),x),x),x),x),x)-a*y(x)=0,y(x))
\[y \left (x \right ) = c_{1} \hypergeom \left (\left [\right ], \left [\frac {6}{5}, \frac {7}{5}, \frac {8}{5}, \frac {9}{5}\right ], -\frac {a}{3125 x^{5}}\right )+c_{2} x \hypergeom \left (\left [\right ], \left [\frac {4}{5}, \frac {6}{5}, \frac {7}{5}, \frac {8}{5}\right ], -\frac {a}{3125 x^{5}}\right )+c_{3} x^{2} \hypergeom \left (\left [\right ], \left [\frac {3}{5}, \frac {4}{5}, \frac {6}{5}, \frac {7}{5}\right ], -\frac {a}{3125 x^{5}}\right )+c_{4} x^{3} \hypergeom \left (\left [\right ], \left [\frac {2}{5}, \frac {3}{5}, \frac {4}{5}, \frac {6}{5}\right ], -\frac {a}{3125 x^{5}}\right )+c_{5} x^{4} \hypergeom \left (\left [\right ], \left [\frac {1}{5}, \frac {2}{5}, \frac {3}{5}, \frac {4}{5}\right ], -\frac {a}{3125 x^{5}}\right )\]