Sometimes we even leave it as "i" instead of "0 < i < n" or "i = 1 to n". Sometimes the range of the summation doesn't even need to be determined in intermediate steps.

There's also this formulation, which I'm quite partial to:

    ---
    \
    /
    ---
  i∈[1,n]

0 < i <= n or upto n-1 respectively.