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%I #15 Jul 05 2023 04:21:34
%S 2,23,317,1031,86453
%N Numbers n such that (10^n-1)/9 is prime, but cannot be written in the form a^2 + 3*b^2.
%C The exponent is congruent to 2 mod 3.
%H Samuel S. Wagstaff, Jr., <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a>
%Y Subsequence of A004023.
%K nonn
%O 1,1
%A _V. Raman_, Sep 08 2012
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