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 $n^2+n+1$ ?

  • 1
    $\begingroup$ What makes you think that the answer to this question is known? $\endgroup$ – John Gowers Jan 23 '18 at 15:11
  • $\begingroup$ If you'd like to know, an affirmative answer to this problem would lead to a breakthrough $\endgroup$ – ArtW Jan 23 '18 at 15:13
  • $\begingroup$ by accident, I was observing uniqueness of positional numeral systems which all digits are same (likewise 111,444,666...) $\endgroup$ – Jay C. Lee Jan 23 '18 at 15:18
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    $\begingroup$ As far as I know there isn't a single example of a non-linear polynomial which is known to take on infinitely many prime values. Of course, there are lots of conjectures regarding this issue, notably The Bunyakovsky conjecture. $\endgroup$ – lulu Jan 23 '18 at 15:22
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    $\begingroup$ Yes, it is a special case of the Bunyakovsky conjecture, see this similar question. $\endgroup$ – Dietrich Burde Jan 23 '18 at 15:23

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