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%I #16 May 02 2013 13:03:36
%S 5,53,293,641,3011
%N Numbers n such that (10^n + 1)/11 is prime, but cannot be written in the form a^2 + 7*b^2.
%C These exponents are congruent to {2, 4, 5} mod 6.
%H Samuel S. Wagstaff, Jr. <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a>
%Y Cf. A001562.
%K nonn
%O 1,1
%A _V. Raman_, Sep 08 2012
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