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A277370 Positive integers n such that n divides 7^n + 2. 6

%I

%S 1,3,15,69,2155,34073,876047637,97090036327,420397381695,

%T 2125899832395,3177544777277,34434175473881,40845965389135

%N Positive integers n such that n divides 7^n + 2.

%C All terms are odd.

%C No other terms below 10^15. Some larger terms: 21419515204636141, 5623143546839445899891, 46186634668308298262543001. - _Max Alekseyev_, Oct 18 2016

%F A066438(a(n)) = a(n) - 2 for n > 1.

%e 7^3 + 2 = 345 = 3 * 115, so 3 is a term.

%t Select[Range[1, 9999, 2], Divisible[7^# + 2, #] &] (* _Alonso del Arte_, Oct 11 2016 *)

%o (PARI) is(n) = Mod(7, n)^n==-2 \\ _Felix Fröhlich_, Oct 14 2016

%Y Cf. A066438.

%Y Cf. Solutions to 7^n == k (mod n): A277371 (k=-3), this sequence (k=-2), A015954 (k=-1), A067947 (k=1), A277401 (k=2), A277554 (k=3).

%K nonn,more

%O 1,2

%A _Seiichi Manyama_, Oct 11 2016

%E a(8)-a(13) from _Max Alekseyev_, Oct 18 2016

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Last modified May 28 21:37 EDT 2020. Contains 334690 sequences. (Running on oeis4.)