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Numbers n such that the n-th Lucas number is prime, but cannot be written in the form a^2 + 7*b^2.
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%I #12 May 02 2013 13:07:21

%S 2,8,11,13,31,41,47,61,79,313,617,863,1097,4793,5851,7741,12251,13963,

%T 35449,36779,44507,89849,140057,148091,202667,387433,443609,574219,

%U 631181,651821

%N Numbers n such that the n-th Lucas number is prime, but cannot be written in the form a^2 + 7*b^2.

%H Blair Kelly, <a href="http://mersennus.net/fibonacci">Factorizations of Fibonacci and Lucas numbers</a>

%Y Cf. A000032, A001606.

%K nonn

%O 1,1

%A _V. Raman_, Sep 08 2012