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%I #4 Jul 03 2020 13:36:55
%S 3,5,11,13,17,43,241,257,331,683,2731,5419,43691,61681,65537,174763,
%T 2796203,15790321,18837001,22366891,715827883,4278255361,4562284561,
%U 77158673929,1133836730401,2932031007403,4363953127297
%N Aurifeuillian primes of the form 2^k+1
%C Take an irreducible real factor of x^k+1 and substitute x=2. If the result is a prime then it belongs in this sequence. For example for k=5 the polynomial x^5+1=(x+1)(x^4-x^3+x^2-x+1) and substituting x->2 in (x^4-x^3+x^2-x+1) we get the prime number 11. So 11 is a term. [Clarified by _N. J. A. Sloane_, Jul 03 2020]
%Y A061442.
%K nonn
%O 1,1
%A _Artur Jasinski_, Dec 26 2008
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