Just to clarify why, if the result is ever one (the loop's exit condition), then it would be about to get stuck repeating 1,4,2 forever if it didn't exit. If you can prove the loop does not exit (i.e., never reaches one) for some n, then you just proved that, for that n, it would never reach the 1,4,2 repetition pattern even without the stop condition.

It's a clever way to re-state the problem to look more computer-science-y.