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%I #11 Mar 30 2012 18:39:04
%S 2,7,23,31,47,71,73,79,89,103,127,151,167,191,199,223,233,239,263,271,
%T 311,337,359,367,383,431,439,463,479,487,503,599,601,607,631,647,719,
%U 727,743,751,823,839,863,881,887,911,919,937,967,983,991,1031,1039,1063
%N Primes p that do not divide 2^x+1 for any x>=1.
%C Also, primes p such that p^2 does not divide 2^x+1 for any x>=1.
%C A prime p cannot divide 2^x+1 if the multiplicative order of 2 (mod p) is odd. - _T. D. Noe_, Aug 22 2004
%C Differs from A049564 first at p=6529, which is the 250th entry in A049564 related to 279^32 =2 mod 6529, but absent here because 6529 divides 2^51+1. [From _R. J. Mathar_, Sep 25 2008]
%D A. K. Devaraj, "Euler's Generalization of Fermat's Theorem-A Further Generalization", in ISSN #1550-3747, Proceedings of Hawaii Intl Conference on Statistics, Mathematics & Related Fields, 2004.
%H T. D. Noe, <a href="/A072936/b072936.txt">Table of n, a(n) for n=1..1000</a>
%Y Cf. A040098, A049096, A014664 (multiplicative order of 2 mod n-th prime).
%K nonn
%O 1,1
%A _Benoit Cloitre_, Aug 20 2002
%E Edited by _T. D. Noe_, Aug 22 2004