duplicate This question about a trigonometric sum is a duplicate IMO: math.stackexchange.com/q/4274129/42969.

@MartinR As far as I can tell from the announcement The Follow Questions and Answers feature is now live across the Network on Meta Stack Exchange, no notification is sent to a user upon un/deletion of a post that they are following. There is also a feature request regarding this, but it hasn't received much activity by way of comments/answers: Notification when a followed post is deleted.

@TheAmplitwist You are right, thanks. Now I remember that I saw that request.

@MartinR No problem :)

So the only way to detect undeleting of that question is to check it from time to time – undelete votes never expire and only one is missing ...

I suppose that's true. Perhaps the moderator tools page has useful tools to keep track of these things, but I wouldn't have any idea about that...

There seems to be an edit war still ongoing at this question: math.stackexchange.com/q/2375092/42969 – Perhaps we should take the opportunity and close it as off-topic?

@MartinR I think that episode has closed, no further edits/rollbacks appear likely.

@Peter It does seem a bit slow here (CURED), lately.

cv-pls computational-complexity PSQ. Compare $O(n^{\log n})$ and $O((\log n)^n)$‭ - lalaland‭ 2021-10-11 18:59:13Z

cv-pls calculus Another similar PSQ. How can we determine the convergence of this improper integral?‭ - Ana‭ 2021-10-10 22:45:41Z

@XanderHenderson I somehow ended up squeezing an answer through here. You had closed it as a duplicate. I was thinking for a long time whether to close this as a duplicate or not, but I felt that for the current context a different kind of answer was required and I prioritized some things that the other post did not. Should I delete my answer?

@XanderHenderson Nevermind. I've closed it as a duplicate.

@TeresaLisbon Meh.

@XanderHenderson I had to look up what "Meh" means, but thanks. If I had to delete it I'd probably have kept it in mind for a good occasion.

@XanderHenderson The answerers did not even notice (or ignored) that there is no "dx" in the integral apart from the lack of context.

C/D

Can someone help me understand how this question lacks details or clarity?

@Tacoタコス There are a couple of things that I can think of (though I have neither downvoted nor flagged for closure). (1) A "series" is technically/mathematically defined as an infinite sum, so the statement 'Are there any series (it doesn't have to be summation) that have a "constant" output...' is a little unclear. Perhaps you mean "sequence", in which case it makes a bit more sense.

(2) However, even changing the word "series" to "sequence", it seems that your question just boils down to 'Is there a constant sequence?', in which case the answer might simply be, 'Sure, the constant sequence is a legitimate sequence.' But that's definitely not what you're after, so I would say your question needs a bit of rewording...

From what I understand, you seem to be interested in whether there is a function f (defined on the positive integers, perhaps) that is specified by some rule (preferably complicated?) that has an apparent dependence on the parameter n, but still the output turns out to be constant for all values of n. I hope I have understood your question correctly?

@Tacoタコス I personally think that everything is in place, but the question can be organized better . Right now I see (1) Question : What kind of iterations/procedures can generate a constant output? (2) Motivation : For designing interesting puzzles, I would say (3) Example : The iteration given makes sense to me. I get an idea for what you want, honestly, and it's been said above as well. Some organization may be required.

Okay, @JoséCarlosSantos, you wanna play games and serial target?

@Tacoタコス I think this question just needs to be phrased in a way such that (1), (2) and (3) are clearly emphasised. Beyond that, those that wish to clarify can interject. By the way, something like this is usually referred to as invariance. For an example something more non-trivial : start with some $(a,b)$ and at each iteration, output $a^2+b^2$ and then change $(a,b)$ to $(0.6a+0.8b,0.8a-0.6b)$. This would produce a constant output, and it's certainly less contrived than the one you gave.

Thank you @TheAmplitwist and @TeresaLisbon I'll take some time and see if I can't figure out how to word smith it to your points. You both understood my intent very clearly, and your points seem very close which means others likely see it the same way. :)

@Tacoタコス Good to know I could be of help.

PSQ.

@MartinR Why was the star for this important message removed ? We should prepare for an undelete of this question , how annoying it would be.

Hopefully that's better :)

@Tacoタコス Will take a look, thanks.

@Tacoタコス I think it's great now, honestly. I've voted up and I don't think I had a close vote in there at all, so , yeah, great!

Thank you for the feedback and help!

I'm not too great with mathematical terminology so I have a bit of a learning curve here :)

@Tacoタコス No problem, feel free to take help when necessary, although you will have the hang of it soon. I saw the answer from Yorch, it looks good and I hope that this has had a good conclusion.

@Peter Can you link to the question not starred now? I'll be happy to star it!

I think I found it, @Peter. Let me know if I got it right (the right question/comment)

@Peter, @MartinR I can pin it for a month or so, so that might help.

Done! It should stay at the top, or in the first two or three listed to the right (only in case of one or two other pinned comments), because pinned comments "rise" above unpinned starred comments.

@amWhy That was it ! Thanks.

@Peter NP

Needs closure