Interpretation of for loop.
Here is the probable interpretation:


  for every $j \neq i$ in $\{0,\ldots,n-1\}$:
  
  &emsp; code


should be interpreted as:


  for every $j$ in $\{0,\ldots,n-1\}$:
  
  &emsp; if $j \neq i$:
  
  &emsp; &emsp; code


This is similar to the way this kind of statement is interpreted in mathematical text.

It is also possible that the roles of $i$ and $j$ should be switched &mdash; this should be clear from context, and it's an ambiguity that also exists in mathematical texts.

As mentioned in Evil's answer, if neither $i$ nor $j$ has been defined, then the interpretation is probably


  for every $i,j$ in $\{0,\ldots,n-1\}$:
  
  &emsp; if $i \neq j$:
  
  &emsp; &emsp; code