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If $n\equiv 2\pmod 3$, then $7\mid 2^n+3$.
In this (btw, nice) answer to Twin primes of form $2^n+3$ and $2^n+5$, it was said that:
If $n\equiv 2\pmod 3$, then $7\mid 2^n+3$?
I'm not familiar with these kind of calculations, so I'd like ...
3
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1answer
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Is this a good proof of Wilson's theorem? — ($(n-1)!+1 \equiv_n 0$ iff n is prime)
Theorem: $(n - 1)! + 1 \equiv_n 0$ if and only if $n$ is prime.
To prove that if $n$ is not prime this is not true is trivial, so I'm just interested in proving that this is true for all p:
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