

A015919


Positive integers n such that 2^n == 2 (mod n).


27



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
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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
Terms of the form 2^k  2 corresponds to k in A296104.  Max Alekseyev, Dec 04 2017
If 2^n1 is a term, then so is n.  Thomas Ordowski, Apr 27 2018


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@370, PowerMod[2, #, #] == 2 &], {1, 2}] // Flatten (* Robert G. Wilson v, May 16 2018 *)


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



