```py
In [1]: summation((-1)**(2*x + 2), (x, 0, n))
Out[1]: nan

In [2]: summation((-2)**(2*x + 2), (x, 0, n))
Out[2]:
   2⋅n + 2
4⋅2          4
────────── - ─
    3        3

In [3]: summation((-2)**(y*x + 2), (x, 0, n))
Out[3]:
  ⎛      n⋅y + y    ⎞
4⋅⎝- (-2)        + 1⎠
─────────────────────
           y
     - (-2)  + 1
```