3:35 AM
A new tag . Created by Intuition.
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Prove that $Z_{p^\infty}$ is the injective envelope of $Z_{p}$, could anyone give me a hint for the proof?

11 hours later…
2:30 PM
The tag is back - due to undeletion.
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We have a set $$M = \{(x,y)\in \mathbb{Z}^2; 0\leq x,y\leq 10\}$$ Let $P$ be a subset of rectangles with vertices in $M$ and with sides parallel to coordinate axis. What is the smallest cardinality of $P$ if we know that we have in $P$ two rectangles $R$ and $R'$ such that $R\subseteq R'$? I k...

I have edited this instance.
Looking at this SEDE query, it seems that the tag with the same name had a shortlived occurrence also in 2013.