I think that this question UN12, which contains also an answer given by me, didn't deserve deletion. I've have also some doubt on closure but I would like some other advice on that.

This one also seems genuinely raised to me UN13. Maybe there is some good duplicate which refer to?

I admit that this one UN14 is not posed in a great way as question but maybe the answer given (by me) could be of some interest.

This question also UN15 to evaluate. Maybe it deserve closure as a duplicate bu tnot deletion. The asker already know the answer and is asking indeed for a proof.

This one UN16 has similar issue to UN13.

This one UN17 maybe deserve closure as duplicate and shoud be formatted properly with mathjax. Unfortunately it was deleted by a moderator and it is not eligible for undeletion. I totally disagree with deletion in this case.

This one UN18 has similar issue of [UN13] and [UN16].

This one UN19 also as the previuos one.

This one UN20 also it is of course elementary but genuinely raised.

This one UN21 as the previous one.

I can't see any good reason why this one UN22 should be closed and deleted.

For this one UN23 the issue is similar to [UN13] and etc. It seems there are many valuable aswers to me.

Since you asked about duplicates for 2672501: Show that $2^{64}-1$ is not prime (UN13). This is no exact duplicate, but a natural generalization, which could have been linked there: If $2^n - 1$ is prime from some integer $n$, prove that n must also be prime.

Disclaimer: note that all the previous submitted questions contain also an answer given by me. Please evaluate carefully all the content and decide if it needs to be preserved as useful. I also would appreciate any observation, advice, thought from other users.

@MartinSleziak Thanks I think it could be a more reasonable motivation to close UN13.

Well, to be honest, UN13 Show that $2^{64}-1$ is not prime seems to me as perfect example for the close reason "missing context". Which is exactly the close reason which was chosen.

@MartinSleziak I aprreciate you have expressed your motivation. it is fair to have different point of view. I see an asker who genuinely needs some help to understand an issue. I can't see anything bad with it. In these case closure suffices and of course some good duplicates can also help the asker. Closure without dulicates and deletion is very bad in my opinion.

If you consider your answer from Point from unit cube and if it adds something to the already existing answers, you could simply post it as an answer to the duplicate target: Probability that a quadratic polynomial with random coefficients has real roots.

@user I don't take your opinion away, but AFAICT it is contrary to the general consensus on the site. Which you surely know - if you read some discussions on meta related to missing context.

@MartinSleziak I'll take a look to these threads and I also would be happy to have more quality in questions but I don't agree with the way often genuinely raised questions are currenty handled. We also need to take into account the "New Contributors" policy and the necessity to make the community more inclusive, enlarge partecipation, be a world wide reference site for math learners (to all levels).

Of course, it is perfectly fine to disagree with the rules of the site you're using. But still, if they are the rules, you should not be surprised if they are enforced. (If you think that they are not good, you could try to persuade other users that they should be changed.)

Anyway, I don't wat to start a lengthy discussion about this now - as I'll have some other stuff to do today (or during the weekend).

@MartinSleziak The community consensus should be expressed primarly by voting system. I see many questions and answer closed and deleted even if upvoted (upvoted=useful content). The opinions expressed in Meta are a good reference but we need first of all to refer to the primary way to judge on that.

You have asked me for links to discussions on meta before - I have posted a few in another room.

@MartinSleziak Yes of course! Thanks for your kind attention and time.

@MartinSleziak Thanks! I'l take a look. Bye

Well, it says that: You have already voted to reopen this question; you may recast your vote in 2 days. Something changed recently? I remember it was only allowed to vote once to reopen/close.

@Zacky From the FAQ post "What is a “closed”, “on hold”, or “duplicate” question?"

> You can only vote to close once per question, unless your vote expired

> You can only vote to reopen once per question, unless your vote expired

It links to this answer: Age close votes after 14 days, regardless of views, allowing recasting

The way I rembember it (but I am not 100% sure is) that:

If I voted to reopen and this actually lead to reopening (i.e., I am among the users who are listed in the history/timeline as the users who reopened the questions), and the question is then closed again, then I am not allowed to cast another reopen vote.

If I voted to reopen and nothing happened (the question was not reopened), I am allowed to case reopen voted again. (And it is the same with close votes.)

Maybe somebody can confirm whether they remember it the same.

I have no objection if the above is moved to Math Meta Chat. (If you don't consider it suitable for this room or you think that it is a better fit over there.)

@MartinSleziak Thank you! I guess I missed that and this scenario rarely happens.

U(115-1),U(115-2),U(115-3),U(115-4)

The last is a dupe FAQ among hundreds oin that topic and will be closed & deleted as such, so why waste everyone's time with such questions?

Can you link some of those hundreds? Or perhaps a good duplicate target? My search might be bad.

U116

U117,U118

@Zacky What search did you try?

I searched the keywords "number","proper","divisors","combinatorics".

@Zacky try: count divisors [combinatorics]

Oh, you used the site search, not approach0. I would also add "is:question" to your query. Anyway which one would be a good duplicate target from there?