A015922 Numbers k such that 2^k == 8 (mod k).

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.

Cf. A015921, A130133, A130134.

Sequence in context: A281089 A242333 A231811 * A212255 A078829 A045583

Adjacent sequences: A015919 A015920 A015921 * A015923 A015924 A015925

Keyword

nonn

Author

Robert G. Wilson v

Extensions

First 5 terms inserted by David W. Wilson

Status

approved