%I #21 Apr 01 2017 09:02:17

%S 1,2,3,4,5,8,9,16,17,21,27,32,45,63,64,99,105,117,124,128,153,171,189,

%T 207,254,256,261,273,279,333,369,387,423,429,477,512,513,531,549,585,

%U 603,639,657,711,747,801,873,909,927,945,963,981,1017,1143,1179,1197,1209,1233,1251,1341,1359,1365,1413,1467,1472,1503,1504,1557,1611,1629,1665,1719,1737,1773,1785,1791,1899,1971

%N Positive integers n such that 2^n (mod n) == 2^9 (mod n).

%C For all m, 2^A128123(m)-1 belongs to this sequence.

%H Seiichi Manyama, <a href="/A015931/b015931.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 Select[Range[2000],PowerMod[2,9,#]==PowerMod[2,#,#]&] (* _Harvey P. Dale_, Apr 01 2017 *)

%o (PARI) isok(n) = Mod(2, n)^n == 2^9; \\ _Michel Marcus_, Sep 23 2016

%Y Contains A208157 as a subsequence.

%Y The odd terms form A276970.

%K nonn

%O 1,2

%A _Robert G. Wilson v_

%E Edited by _Max Alekseyev_, Jul 30 2011

%E Definition clarified by _Harvey P. Dale_, Apr 01 2017