Why my duplicate flag is declined?

Aren't these questions similar?

Factorial Proof by Induction Question: $\frac1{2!} + \frac2{3!} + \dots+ \frac{n}{(n+1)!} = 1 - \frac1{(n+1)!}$?

Prove if $n \in \mathbb N$, then $\frac{1}{2!}+\cdots+\frac{n}{(n+1)!}=1-\frac{1}{(n+1)!}$

I flagged the first one as duplicated but it is declined. Why? I know that it happens when three users voted to let it open. But why they do that is the exactly same.

edit1: I flagged the first one.

edit2: There is also another question that is exactly the same see: Proof by induction that $\sum_{i=1}^n \frac{i}{(i+1)!}=1- \frac{1}{(n+1)!}$ I think the other others should be duplicate of this also the first one because this is older than the others and it has more up votes.

• There should be a reason included on why it was declined. Did you read it? Commented Jul 10, 2016 at 9:13
• @J. M.There isn't anything. Commented Jul 10, 2016 at 9:14
• @J.M. There's a decline-reason if and only if the flag is declined by a moderator. If the flag is declined via review-queue actions, there's just the outcome, no reason. Commented Jul 10, 2016 at 9:19
• In which case, @Daniel, I would submit that it is a rather annoying feature. How is the flagger supposed to know how s/he messed up? Or worse, if the decliners were actually in error because they couldn't be arsed to check? Commented Jul 10, 2016 at 9:22
• I can't tell you why the reviewers voted to leave open, but I agree that the two are duplicates. Commented Jul 10, 2016 at 9:22
• I agree with Taha Akbari. The two questions are undoubtedly duplicates. Daniel beat me to closing the later (and less upvoted) version as a duplicate of the other while I was having fun commenting that IMO calculating the value of a telescoping sum is a proof by induction :-) Commented Jul 10, 2016 at 9:27
• @J.M. Indeed that's not ideal. But having moderators vet every flag that would be review-declined wouldn't fly on SO (and even here, that would create a lot of additional work for the moderators). But having a message "declined - from review" or similar might be an improvement over the current situation. Commented Jul 10, 2016 at 9:33
• None of that sort, @Daniel. :) A "declined - from review" plus a link to the particular review page for that flag was what I had envisioned. But I am loathe to ask in meta.SE; oh well… Commented Jul 10, 2016 at 9:46
• @J.M. I'm going to search a bit, and if I don't find anything, I may post a feature request over there. Commented Jul 10, 2016 at 9:51
• Commented Jul 10, 2016 at 9:54
• Probably it would be better to choose a duplicate target which is not (proof-verification) request. Like this one. Commented Jul 10, 2016 at 10:40
• BTW here is link to the review. Commented Jul 10, 2016 at 10:47
• A reason could be they did not realize it was a duplicate closure that was proposed, and they thought it was a regular one. This is not unheard of.
– quid
Commented Jul 10, 2016 at 11:43
• There are many possible explanations. (All of them pure speculation, unless they come directly from users who voted.) Here are two possibilities: 1) Proof-verification questions are usually closed as duplicates only after the OP have received sufficient feedback. So it is customary to leave some time. 2) If the reviewers opened the question in new window, they saw that there are no close votes. (The reason is that it was flagged, not close-voted). But they might have been suspicious that it is a review audit, so they decided to stay on the safe side. Commented Jul 10, 2016 at 12:12
• "If the reviewers opened the question in new window, they saw that there are no close votes. (The reason is that it was flagged, not close-voted)." - I admittedly did not account for that mechanism, @Martin; so in this case, it behooves the flagger to leave a comment that s/he thinks this is a dupe. A slight annoyance, admittedly, but I suppose we have to make do. Commented Jul 10, 2016 at 12:15