%I A127958
%S A127958 4,7,10,12,13,14,16,17,18,19,20,22,23,24,25,26,27,28,29,31,32,33,34,35,
%T A127958 36,37,38,40,41,42,43,44,45,46,47,48,49,51,52,53,54,55,56,57,58,59,60,
%U A127958 61,62,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,84,85
%N A127958 Numbers x such 1+Sum[2^(2n-1]] is not prime for n=1,2,...,x.
%C A127958 Numbers x such 1+Sum[2^(2n-1]] is prime for n=1,2,...,x gives A127936.
%t A127958 a = {}; Do[If[PrimeQ[1 + Sum[2^(2n - 1), {n, 1, x}]] == False, AppendTo[a, 
               x]], {x, 1, 1000}]; a
%Y A127958 Cf. A000979, A000978, A124400, A126614, A127955, A127957, A127936.
%Y A127958 Sequence in context: A082206 A115566 A087298 this_sequence A000414 A025357 
               A144020
%Y A127958 Adjacent sequences: A127955 A127956 A127957 this_sequence A127959 A127960 
               A127961
%K A127958 nonn
%O A127958 1,1
%A A127958 Artur Jasinski (grafix(AT)csl.pl), Feb 09 2007