%I A127956
%S A127956 29,37,41,47,53,59,67,71,73,83,89,97,103,107,109,113,131,137,139,149,
%T A127956 151,157,163,173,179,181,193,197,211,223,227,229,233,239,241,251,257,
%U A127956 263,269,271,277,281,283,293,307,311,317,331,337,349,353,359,367,373
%N A127956 Prime numbers p such that (2^p+1)/3 is composite.
%C A127956 If p-1 is squarefree, 2a(n) is the multiplicative order of 2 modulo every 
               divisor d>1 of (2^p+1)/3. - Vladimir Shevelev (shevelev(AT)bgu.ac.il), 
               Jul 15 2008
%t A127956 a = {}; Do[c = (2^Prime[x] + 1)/3; If[PrimeQ[c] == False, AppendTo[a, 
               Prime[x]]], {x, 2, 100}]; a
%Y A127956 Cf. A000979, A000978, A124400, A126614, A127955, A127957.
%Y A127956 Sequence in context: A134254 A089296 A089297 this_sequence A166088 A161724 
               A046502
%Y A127956 Adjacent sequences: A127953 A127954 A127955 this_sequence A127957 A127958 
               A127959
%K A127956 nonn
%O A127956 1,1
%A A127956 Artur Jasinski (grafix(AT)csl.pl), Feb 09 2007