\[ y^{(n)}(x)-f\left (y^{(n-2)}(x)\right )=0 \] ✗ Mathematica : cpu = 0.00366543 (sec), leaf count = 0 , could not solve
DSolve[-f[Derivative[-2 + n][y][x]] + Derivative[n][y][x] == 0, y[x], x]
✗ Maple : cpu = 0. (sec), leaf count = 0 , exception
unable to handle ODEs of undefined differential order