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%I #12 Jul 30 2020 03:58:57
%S 2921,3017,3473,3479,5767,5969,6167,6377,6497,6913,7223,7519,7567,
%T 7751,9017,9271,10199,10447,11431,11929,12719,13439,13609,14513,16583,
%U 17009,17143,18631,18809,19313,20737,21119,22337,22351,22537
%N Numbers k > 1 such that k mod ord2(k) is even, where ord2(k) is the order of 2 mod k.
%C These are all composite since for prime p, ord2(p) | phi(p) = p-1, whence p mod ord2(p) = 1.
%H Amiram Eldar, <a href="/A036260/b036260.txt">Table of n, a(n) for n = 1..10000</a>
%t Select[Range[3, 23000, 2], EvenQ[Mod[#, MultiplicativeOrder[2, #]]] &] (* _Amiram Eldar_, Jul 30 2020 *)
%Y Cf. A002326, A007733, A036259.
%K nonn
%O 1,1
%A _David W. Wilson_
%E Offset corrected by _Amiram Eldar_, Jul 30 2020
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