I think it is reasonable to leave at least 24 hours. (So that people who visit this room can write here, if they have something to say about that.)

Of course, if somebody thinks it's already time to vote, I have no objections. (Although I do not see a reason to hurry, either. Those questions were lying around without being close for a few years. Unless I missed something, there wasn't some new activity on them since I posted the links.)

PSQ: math.stackexchange.com/q/3475535/137524

@MartinSleziak Ah. I had thought that you might have posted elsewhere. I have not changed my mind; I just wanted to make sure that the comments did not get lost.

duplicates These two questions seem to be duplicates (both ask about the same integral and about polar coordinates). 1793975: Integral conversion to polar coordinates - bounds $\int\limits_0^1 \int\limits_0^1\sqrt{x^2+y^2}\ dxdy$ and 3475788: Evaluating $\int_{0}^{1}\int_{0}^{1}\sqrt{x^{2}+y^{2}}dxdy$ using polar coordinates.

I would not be surprised if there are other copies of the same problem, this was what I was able to find among top results in Approach0 and in SearchOnMath.

@MartinSleziak Since nobody objected, I went with Xander Henderson's suggestion and cast close votes with the oldest post as the duplicate target. I have also edited the title: How do you solve a recurrence with a summation function inside: $t(n) = 1 + \sum\limits_{j=0}^{n-1} t(j)$. (In order to make the title more descriptive - so that if the post is shown in some list of questions, the contend is clearer directly from the title.)

Same question posted twice by user: math.stackexchange.com/q/3475772/137524, math.stackexchange.com/q/3475509/137524

That said, neither question has an answer yet. So it’s not correct to close one as a dupe of the other.

(There are good reasons to close both regardless)

D1, D2, D3.

D4, D5, D6.

D7, D8, D9.

D10, D11, D12.

D13, D14, D15.

@Semiclassical A question can be closed as a duplicate of another question of the same author even if the target has no answers.

Ah.

math.stackexchange.com/help/duplicates: questions may only be marked as duplicates of unanswered questions on meta sites, when the questions share the same author, or when closed by a moderator.

[ SmokeDetector | MS ] Url in title, potentially bad keyword in title (97): $f:\mathbb{Z}/6\mathbb{Z} \longrightarrow \mathbb{Z}/3\mathbb{Z} \times \mathbb{Z}/2\mathbbmath.stackexchange.com/users{Z}$ group morphism? by Kyle Yarbrough on math.SE