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A273949 Odd prime factors of generalized Fermat numbers of the form 11^(2^m) + 1 with m >= 0.

%I A273949 #13 Jun 17 2016 02:23:31
%S A273949 3,17,61,193,257,7321,15361,51329,65537,163841,6304673,15190529,
%T A273949 70254593,1691123713,1760464897,3221225473,3489660929,4696846849,
%U A273949 6874464257,53401878529,111489577217,149300051969,184683593729,206158430209,447600088289,1819992391681
%N A273949 Odd prime factors of generalized Fermat numbers of the form 11^(2^m) + 1 with m >= 0.
%C A273949 Odd primes p other than 5 such that the multiplicative order of 11 (mod p) is a power of 2.
%D A273949 Hans Riesel, Common prime factors of the numbers A_n=a^(2^n)+1, BIT 9 (1969), pp. 264-269.
%H A273949 Arkadiusz Wesolowski, <a href="/A273949/b273949.txt">Table of n, a(n) for n = 1..31</a>
%H A273949 Anders Björn and Hans Riesel, <a href="http://dx.doi.org/10.1090/S0025-5718-98-00891-6">Factors of generalized Fermat numbers</a>, Math. Comp. 67 (1998), no. 221, pp. 441-446.
%H A273949 Anders Björn and Hans Riesel, <a href="http://dx.doi.org/10.1090/S0025-5718-05-01816-8">Table errata to “Factors of generalized Fermat numbers”</a>, Math. Comp. 74 (2005), no. 252, p. 2099.
%H A273949 Anders Björn and Hans Riesel, <a href="http://dx.doi.org/10.1090/S0025-5718-10-02371-9">Table errata 2 to "Factors of generalized Fermat numbers"</a>, Math. Comp. 80 (2011), pp. 1865-1866.
%H A273949 Harvey Dubner and Wilfrid Keller, <a href="http://dx.doi.org/10.1090/S0025-5718-1995-1270618-1">Factors of Generalized Fermat Numbers</a>, Math. Comp. 64 (1995), no. 209, pp. 397-405.
%H A273949 OEIS Wiki, <a href="/wiki/Generalized_Fermat_numbers">Generalized Fermat numbers</a>
%t A273949 Delete[Select[Prime@Range[2, 10^5], IntegerQ@Log[2, MultiplicativeOrder[11, #]] &], 2]
%Y A273949 Cf. A023394, A072982, A199592, A273945 (base 3), A273946 (base 5), A273947 (base 6), A273948 (base 7), A273950 (base 12).
%K A273949 nonn
%O A273949 1,1
%A A273949 _Arkadiusz Wesolowski_, Jun 05 2016