# Should a closed question be reopened if it gets a duplicate?

This question How do you prove that $n^2-1$ is composite when $n>2$? was closed as a duplicate. That was the right outcome, as opposed to, you know, "off-topic."

But the question it's a duplicate of is closed! Prove that there doesn't exist any integer $x \ge 3$ such that $x^2-1$ is prime. At least it does have one answer, but that answer, as obvious as it might seem to most of us, is borderline impenetrable to the site's more casual visitors.

Not that the closed question's asker would care one way or the other, but I think other people who happen to come across either of these pages would appreciate one of them having a slightly elaborated answer.

I'm not proposing that duplicates should automatically reopen closed questions, that would probably lead to more questions that should be closed as duplicates being closed for some silly reason instead.

What I'm asking is: does there exist the possibility, on a case-by-case basis, to reopen a closed question if it's identified as the original for a duplicate question?

• The possibility exists. But usually, one should first try to look for a better duplicate target. For "$n^2 - 1$ is rarely prime", we must have quite a few instances. Hopefully at least one of them isn't poor. – Daniel Fischer Jul 1 '18 at 19:40
• this one looks a bit better – user99914 Jul 1 '18 at 19:51
• This one too. – Daniel Fischer Jul 1 '18 at 19:54
• As of this point, at the time of this comment, (which is $2$ hours after Robert posted this question), the question in question points now to two duplicates, both of which are open. The list of dupes was altered by a mod, since there were many good representatives to serve as a higher quality dupe target, likely as a result of your question here, @Robert. – amWhy Jul 1 '18 at 21:38
• Thank you, @amWhy, for the update. – Robert Soupe Jul 1 '18 at 23:19
• I have created (a rather simplistic) SEDE query which looks for questions that are closed and the duplicate target is closed, too. I have mentioned it in Math Meta chat room - perhaps somebody will suggest some improvements to the query. – Martin Sleziak Jul 2 '18 at 15:34
• @MartinSleziak I urge you to post it here as an answer so that people can maybe contribute here to such a discussion. It feels like something that might be useful to this question. – user64742 Jul 7 '18 at 18:46