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%I #6 Sep 08 2012 15:24:15
%S 1,5,7,11,13,17,19,23,31,35,43,49,53,61,67,77,79,85,89,91,101,119,121,
%T 127,133,139,161,167,179,187,191,199,211,215,217,221,223,227,245,269,
%U 301,313,317,323,343,347,361,371,389,395,427,431,433,457,469,503,539
%N Odd numbers n such that (2^n+1)/3 can be written in the form a^2+7*b^2.
%C These numbers of the form (2^n+1)/3 have no prime factors congruent to 3 (mod 7) or 5 (mod 7) or 6 (mod 7) to an odd power. Also the power of 2 is not 1.
%H V. Raman, <a href="/A216523/b216523.txt">Table of n, a(n) for n = 1..83</a>
%H Samuel S. Wagstaff, Jr. <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a>
%K nonn
%O 1,2
%A _V. Raman_, Sep 08 2012