[smadge]

Some authors might prefer

  --
  \
  /
  --
  0 < i < n

Ass opposed to

  n
  --
  \
  /
  --
  i = 1

[vlasev]

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.

[EvilTerran]

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

    ---
    \
    /
    ---
  i∈[1,n]

[abhishekjha]

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