A basic loop written in tex

while_loop.tex

  % NOTE: I do not guarantee that this is the best way of doing it
  % but I wanna share it anyways since I can't really find any (commented) example code like this.
 
  % --- 
 
  % command to print numbers one per line
	% paste somewhere into your document (can be preamble or document itself)
  
	% init counter variable
	\newcount\i
	
	% define macro with one input (integer)
	\def\basicLoop#1{
	
	% init loop with breaking condition - kind of a whiel loop
	% check if counter is less than input
	\loop \ifnum \i < #1
	
	% print counter 
	\number\i
	
	% increment i by one
	\advance\i by 1
	
	% go to the beginning
	\repeat
	
	% print word done
	done
	}
  
  % call function
  \basicLoop{4}

If you'd like to lean more about tex programming, have a look at the answer of this question.

https://tex.stackexchange.com/questions/12668/where-do-i-start-latex-programming

If you'll need to to the whole code as a one-liner to print the numbers in one line.