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A015919 Positive integers n such that 2^n == 2 (mod n). 17
1, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 341, 347, 349, 353, 359, 367 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Includes 341 which is first pseudoprime to base 2 and distinguishes sequence from A008578.

First composite even term is a(14868) = 161038 = A006935(2). - Max Alekseyev, Feb 11 2015

If n is a term, then so is 2^n - 1. - Max Alekseyev, Sep 22 2016

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..20000

FORMULA

A015919 = {1} U A000040 U A001567 U A006935 = A001567 U A006935 U A008578. - Ray Chandler, Dec 07 2003; corrected by Max Alekseyev, Feb 11 2015

MATHEMATICA

Prepend[Select[Range[1000], Mod[2^#, #] == 2 &], 1] (* Geoffrey Critzer, Apr 29 2015 *)

PROG

(PARI) is(n)=Mod(2, n)^n==2 \\ Charles R Greathouse IV, Mar 11 2014

CROSSREFS

Contains A002997 as a subsequence.

The odd terms form A176997.

Cf. A000040, A001567, A008578.

Sequence in context: A216886 A273960 A100726 * A064555 A216887 A095320

Adjacent sequences:  A015916 A015917 A015918 * A015920 A015921 A015922

KEYWORD

nonn

AUTHOR

Robert G. Wilson v

STATUS

approved

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Last modified December 9 00:45 EST 2016. Contains 278959 sequences.