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A015951 Numbers n such that n | 5^n + 1. 15
1, 2, 3, 9, 21, 26, 27, 63, 81, 147, 189, 243, 338, 441, 567, 609, 729, 903, 1029, 1323, 1378, 1701, 1827, 2187, 2667, 2709, 3087, 3969, 4263, 4394, 4401, 5103, 5481, 6321, 6561, 7203, 8001, 8127, 9261, 9429, 11907, 12789, 13149, 13203 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..500

MATHEMATICA

Select[Range@ 14000, Divisible[5^# + 1, #] &] (* Michael De Vlieger, Oct 10 2016 *)

PROG

(PARI) isok(n) = Mod(5, n)^n == -1; \\ Michel Marcus, Oct 11 2016

CROSSREFS

Cf. this sequence (k=1), A123052 (k=3), A123047 (k=4).

Sequence in context: A036673 A111189 A001004 * A244666 A101531 A099607

Adjacent sequences:  A015948 A015949 A015950 * A015952 A015953 A015954

KEYWORD

nonn

AUTHOR

Robert G. Wilson v

STATUS

approved

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Last modified February 21 21:41 EST 2018. Contains 299427 sequences. (Running on oeis4.)