A192109 Numbers k that divide 2^(k-1) - 2.

1, 2, 6, 10, 14, 22, 26, 30, 34, 38, 46, 58, 62, 74, 82, 86, 94, 106, 118, 122, 134, 142, 146, 158, 166, 170, 178, 182, 194, 202, 206, 214, 218, 226, 254, 262, 274, 278, 298, 302, 314, 326, 334, 346, 358, 362, 382, 386, 394, 398, 422, 446, 454, 458, 466, 478, 482, 502, 514, 526, 538, 542, 554, 562, 566, 586, 614, 622, 626

Offset: 1

Author

Max Alekseyev, Apr 22 2013

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Reinhard Zumkeller)

Crossrefs

Contains A216090 as subsequence.

Subsequence of A015921, consisting of the terms that are not multiples of 4.

The odd terms form A173572.

Cf. A014741, A000918.

Programs

Haskell

import Data.List (elemIndices)
a192109 n = a192109_list !! (n-1)
a192109_list = map (+ 1) $ elemIndices 0 $ zipWith mod a000918_list [1..]
-- Reinhard Zumkeller, Apr 23 2013

Mathematica

Join[{1,2},Select[Range[700],PowerMod[2,#-1,#]==2&]] (* Harvey P. Dale, May 15 2015 *)

PARI

is(n)=Mod(2,n)^(n-1)==2 \\ Charles R Greathouse IV, Nov 04 2016