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 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 (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 Terms of the form 2^k - 2 corresponds to k in A296104. - Max Alekseyev, Dec 04 2017 If 2^n-1 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 STATUS approved

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Last modified December 18 21:01 EST 2018. Contains 318245 sequences. (Running on oeis4.)