A277370 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A277370

Positive integers k that divide 7^k + 2.

6

1, 3, 15, 69, 2155, 34073, 876047637, 97090036327, 420397381695, 2125899832395, 3177544777277, 34434175473881, 40845965389135

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

All terms are odd.

No other terms below 10^15. Some larger terms: 21419515204636141, 5623143546839445899891, 46186634668308298262543001. - Max Alekseyev, Oct 18 2016

LINKS

Table of n, a(n) for n=1..13.

FORMULA

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

EXAMPLE

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

MATHEMATICA

Select[Range[1, 9999, 2], Divisible[7^# + 2, #] &] (* Alonso del Arte, Oct 11 2016 *)

PROG

(PARI) is(n) = Mod(7, n)^n==-2 \\ Felix Fröhlich, Oct 14 2016

CROSSREFS

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).

Sequence in context: A110211 A167874 A318967 * A213140 A245751 A033876

Adjacent sequences: A277367 A277368 A277369 * A277371 A277372 A277373

KEYWORD

nonn,more

AUTHOR

Seiichi Manyama, Oct 11 2016

EXTENSIONS

a(8)-a(13) from Max Alekseyev, Oct 18 2016

STATUS

approved