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A015921 Positive integers n such that 2^n == 4 (mod n). 18
1, 2, 4, 6, 10, 12, 14, 22, 26, 30, 34, 38, 46, 58, 62, 74, 82, 86, 94, 106, 118, 122, 132, 134, 142, 146, 158, 166, 170, 178, 182, 194, 202, 206, 214, 218, 226, 254, 262, 274, 278, 298, 302, 314, 326, 334, 346, 358, 362, 372, 382, 386, 394, 398, 422, 446 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Odd terms are given by A173572.
For all m, 2^A050259(m)-1 belongs to this sequence.
LINKS
OEIS Wiki, 2^n mod n
MATHEMATICA
Select[Range[500], PowerMod[2, #, #] == 4 &] (* Alonso del Arte, Jul 07 2011 *)
CROSSREFS
Contains A050990 as a subsequence.
Sequence in context: A301646 A024892 A087136 * A232964 A348442 A132631
KEYWORD
nonn
AUTHOR
EXTENSIONS
Edited and terms 1,2,4 prepended by Max Alekseyev, Jul 29 2011
STATUS
approved

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Last modified March 28 10:31 EDT 2024. Contains 371240 sequences. (Running on oeis4.)