%I A049883
%S A049883 3,5,11,43,683,2731,43691,174763,2796203,715827883,2932031007403,
%T A049883 768614336404564651,201487636602438195784363,
%U A049883 845100400152152934331135470251,56713727820156410577229101238628035243
%N A049883 Primes in the Jacobsthal sequence (A001045).
%C A049883 All a(n), except a(2) = 5, are of the form (2^p + 1)/3 - the Wagstaff 
               primes A000979[n] = {3,11,43,683,2731,43691,174763,...}. Indices 
               of prime Jacobsthal numbers are listed in A107036[n] = {3,4,5,7,11,
               13,17,19,23,31,43,61,...}. For n>1 A107036[n] = A000978[n] Numbers 
               n such that (2^n + 1)/3 is prime. - Alexander Adamchuk (alex(AT)kolmogorov.com), 
               Oct 10 2006
%Y A049883 Cf. A001045, A107036, A000978, A000979.
%Y A049883 Sequence in context: A055511 A105236 A144467 this_sequence A059242 A004203 
               A088884
%Y A049883 Adjacent sequences: A049880 A049881 A049882 this_sequence A049884 A049885 
               A049886
%K A049883 nonn
%O A049883 1,1
%A A049883 Judson D. Neer (judson(AT)poboxes.com)