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Positive integers n such that 2^n == 2^11 (mod n).
10

%I #20 Oct 08 2018 18:13:44

%S 1,2,3,4,8,11,14,15,16,31,32,35,51,56,64,121,128,146,224,256,341,451,

%T 455,496,508,512,671,781,896,1024,1111,1235,1271,1441,1547,1661,1736,

%U 1991,2048,2091,2101,2321,2651,2761,2981,3091,3421,3584,3641,3731,3751,4064,4088,4403,4411,4631,4741,5071,5401,5731,5951,6171,6191,6281,6386,6611,6851,6941,7051,7271,7601,7711,7936,8261,8371,8435,8456,8921

%N Positive integers n such that 2^n == 2^11 (mod n).

%C For all m, 2^A128124(m)-1 belongs to this sequence.

%H Seiichi Manyama, <a href="/A015935/b015935.txt">Table of n, a(n) for n = 1..10000</a>

%H OEIS Wiki, <a href="/wiki/2^n mod n">2^n mod n</a>

%t m = 2^11; Join[Select[Range[m], Divisible[2^# - m, #] &],

%t Select[Range[m + 1, 10^6], PowerMod[2, #, #] == m &]] (* _Robert Price_, Oct 08 2018 *)

%o (PARI) isok(n) = Mod(2, n)^n == Mod(2, n)^11; \\ _Michel Marcus_, Oct 08 2018

%Y The odd terms form A276971.

%K nonn

%O 1,2

%A _Robert G. Wilson v_

%E Edited by _Max Alekseyev_, Jul 30 2011