\[ -3 x (p+q) y''(x)+3 p (3 q+1) y'(x)+x^2 y^{(3)}(x)+x^2 (-y(x))=0 \] ✓ Mathematica : cpu = 0.361604 (sec), leaf count = 135
DSolve[-(x^2*y[x]) + 3*p*(1 + 3*q)*Derivative[1][y][x] - 3*(p + q)*x*Derivative[2][y][x] + x^2*Derivative[3][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to c_1 \, _0F_2\left (;\frac {2}{3}-p,\frac {1}{3}-q;\frac {x^3}{27}\right )+c_2 (-1)^{\frac {1}{3} (3 p+1)} 3^{-3 p-1} x^{3 p+1} \, _0F_2\left (;p+\frac {4}{3},p-q+\frac {2}{3};\frac {x^3}{27}\right )+c_3 (-1)^{\frac {1}{3} (3 q+2)} 3^{-3 q-2} x^{3 q+2} \, _0F_2\left (;q+\frac {5}{3},-p+q+\frac {4}{3};\frac {x^3}{27}\right )\right \}\right \}\] ✓ Maple : cpu = 0.194 (sec), leaf count = 77
dsolve(x^2*diff(diff(diff(y(x),x),x),x)-3*(p+q)*x*diff(diff(y(x),x),x)+3*p*(3*q+1)*diff(y(x),x)-x^2*y(x)=0,y(x))
\[y \left (x \right ) = c_{1} \hypergeom \left (\left [\right ], \left [-q +\frac {1}{3}, -p +\frac {2}{3}\right ], \frac {x^{3}}{27}\right )+c_{2} x^{3 p +1} \hypergeom \left (\left [\right ], \left [p +\frac {4}{3}, \frac {2}{3}-q +p \right ], \frac {x^{3}}{27}\right )+c_{3} x^{3 q +2} \hypergeom \left (\left [\right ], \left [q +\frac {5}{3}, \frac {4}{3}+q -p \right ], \frac {x^{3}}{27}\right )\]