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A015922
Numbers k such that 2^k == 8 (mod k).
20
1, 2, 3, 4, 8, 9, 15, 21, 33, 39, 51, 57, 63, 69, 87, 93, 111, 123, 129, 141, 159, 177, 183, 195, 201, 213, 219, 237, 248, 249, 267, 291, 303, 309, 315, 321, 327, 339, 381, 393, 399, 411, 417, 447, 453, 471, 489, 501, 519, 537, 543, 573, 579, 591, 597, 633
OFFSET
1,2
COMMENTS
For all m, 2^A015921(m) - 1 belongs to this sequence.
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..29055 (first 6822 terms from Zak Seidov)
OEIS Wiki, 2^n mod n.
MATHEMATICA
a015922Q[n_Integer] := If[Mod[2^n, n] == Mod[8, n], True, False];
a015922[n_Integer] :=
Flatten[Position[Thread[a015922Q[Range[n]]], True]];
a015922[1000000] (* Michael De Vlieger, Jul 16 2014 *)
m = 8; Join[Select[Range[m], Divisible[2^# - m, #] &], Select[Range[m + 1, 10^3], PowerMod[2, #, #] == m &]] (* Robert Price, Oct 12 2018 *)
Join[{1, 2, 3, 4, 8}, Select[Range[650], PowerMod[2, #, #]==8&]] (* Harvey P. Dale, Aug 22 2020 *)
PROG
(PARI) isok(n) = Mod(2, n)^n == Mod(8, n); \\ Michel Marcus, Oct 13 2013, Jul 16 2014
CROSSREFS
Contains A033553 as a subsequence.
The odd terms form A276967.
Sequence in context: A281089 A242333 A231811 * A373725 A212255 A078829
KEYWORD
nonn
EXTENSIONS
First 5 terms inserted by David W. Wilson
STATUS
approved