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When $n>3$, $n$ must be $\equiv 0, 2 \pmod 6$
$3$, $7$, $43$, $73$, $157$, $211$, and $421$ are primes,
but $343=7^3$ ($n=18$) is not.
Are there infinitely many primes of the form $n^2+n+1$ ?
Required, but never shown
1 year, 1 month ago