A216555 - OEIS

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A216555

Numbers n such that the n-th Lucas number is prime, but cannot be written in the form a^2 + 3*b^2.

%I #12 May 02 2013 13:09:24

%S 0,5,7,8,13,16,31,37,47,53,61,71,79,503,613,863,7741,19469,81671,

%T 94823,344293,532277,631181,637751,651821

%N Numbers n such that the n-th Lucas number is prime, but cannot be written in the form a^2 + 3*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 1,2

%A _V. Raman_, Sep 08 2012