\[ a^3 x^3 y(x)+3 a^2 x^2 y'(x)+3 a x y''(x)+y^{(3)}(x)=0 \] ✓ Mathematica : cpu = 0.012493 (sec), leaf count = 72
DSolve[a^3*x^3*y[x] + 3*a^2*x^2*Derivative[1][y][x] + 3*a*x*Derivative[2][y][x] + Derivative[3][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to c_1 e^{-\frac {a x^2}{2}}+c_2 e^{-\frac {a x^2}{2}-\sqrt {3} \sqrt {a} x}+c_3 e^{\sqrt {3} \sqrt {a} x-\frac {a x^2}{2}}\right \}\right \}\] ✓ Maple : cpu = 0.035 (sec), leaf count = 37
dsolve(diff(diff(diff(y(x),x),x),x)+3*a*x*diff(diff(y(x),x),x)+3*a^2*x^2*diff(y(x),x)+a^3*x^3*y(x)=0,y(x))
\[y \left (x \right ) = {\mathrm e}^{-\frac {a \,x^{2}}{2}} \left (c_{1}+c_{2} {\mathrm e}^{\sqrt {3}\, \sqrt {a}\, x}+c_{3} {\mathrm e}^{-\sqrt {3}\, \sqrt {a}\, x}\right )\]