@Fundamental gone

@Fundamental That question now has a post no meta.

However, I am not sure whether something reasonable will come from the discussion there.

About the questions on pentagonal and triangular numbers mentioned by @anorton.

The question asks for references. I would like the question much more if online resources were not excluded.

But I still think that the question can be reasonable answered with some amount of effort.

We could check the books which have something on those numbers.

We could check Google Scholar.

OEIS has some references

One book is mentioned on mathworld.wolfram.com/PentagonalTriangularNumber.html

Although it is somewhat unclear whether the OP is looking for references with solution of the above problem, or they only want solutions which use the lemma in the original post.

@DanielFischer One person's standard fact might be another person's difficult problem. (I am certain that many of the questions I have asked would be considered standard exercises by people who are smarter than me.)

Re: What would be gained by undeletion? Recently we have mentioned this question on meta. (Will Jagy was looking for it, you posted an answer with a link.) I'd like to think that my CW-answer there, which is simply a list of references containing solution to that problem, might be useful for some users. (Despite the fact that other posts contain a complete solution.)

I am not saying that this question has to be undeleted. I am just saying that it is not entirely uninteresting. (Although the questions asking for both solutions to the problem and references might be better.)

The last sentence I wrote might suggest that alternative solution would be repost the question instead. And formulate the new version in a way which asks for both, solutions to the problem and references.

@anorton Regarding the Hacker Cup questions (I guess that round is over now), did you have a publicly available URL for the problems themselves? I know about the Facebook page, but from there I wasn't able to access the actual problems (didn't do any of the qual round questions).

(I will admit that I feel much less inclined to lock these questions according to our "policy of contest questions" and this feeling extends to many other online contests.)

Hi, Could you please tell me what mistake I am making in asking this

@MartinSleziak The topic is not uninteresting. But as you mentioned, the exclusion of online resources and in situ proofs is not optimal. Even so, it's not a bad question. But the OP decided to delete it himself. The last point is what makes me hesitant, in particular since I expect the fact would be mentioned and proved in lots of introductory number theory books. If that expectation is wrong, that would be a reason to override the author's decision to delete.

But since you mentioned reposting: A question of that kind that could be answered with a proof and references to papers, books and online sources [of good enough repute] may be the superior alternative.

@ArthurFischer No public link... I'll make sure to find public links for future flags like that.

Hi, It says a moderator has deleted my Question. Here is my Question. I think it's a fair question to ask

math.stackexchange.com/questions/1110174/…

@novice Some background: Your question has a score of -10 (breakdown: +1/-11), five non-moderator users voted to close it, and then a moderator deleted it. (As an aside: only a moderator can undelete it, since moderator deletion votes are binding.)

(in case someone else comes along)

Yeah, but the question is genuine. Just a little hard to get to the depth. It's a genuine question.

Could you please perhaps reconsider, after reading the whole thing.

But I guess it is not necessary - some of the mods will probably notice your message in this room.

alright, thanks a ton.!

There's nothing to thank for. (I suppose either of the two rooms is appropriate for such inquiry.)

I would not be very optimistic about the fate of your post. Even if some of the mods undeletes it, it's probable that regular users will delete it again.

Once again about the question on simultaneously pentagonal and triangular numbers which was mentioned here and here.

Now I found this question: How to find solutions of $x^2-3y^2=-2$? which asks more-or-less the same thing.

So if somebody wants to compile some kind of list of references for this as I suggested, it is possible to post it there. (And it is not necessary to create a new question or undelete that old post.)