%I A139689
%S A139689 0,1,1,0,1,0,1,0,0,1,0,0,1,0,0,1,0,1,0,0,1,1,0,0,0,0,1,0,1,0,0,1,0,1,1,
%T A139689 0,0,1,0,1,0,0,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,1,0,0,1,0,0,0,0,0,0,0,1,
%U A139689 0,0,0,1,0,0,0,1,1,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,1,1,0,0,1,0,0,1,0
%N A139689 If (n-th Chen prime) + 2 is a prime then 1 else 0.
%C A139689 a(n) = A010051(A139690(n)) = 1 - A064911(A139690(n)).
%H A139689 R. Zumkeller, <a href="b139689.txt">Table of n, a(n) for n = 1..1000</
               a>
%H A139689 <a href="Sindx_Ch.html#char_fns">Index entries for characteristic functions</
               a>
%H A139689 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               ChenPrime.html">Chen Prime</a>
%F A139689 a(n) = 2 - A001222(A139690(n)).
%Y A139689 Sequence in context: A010051 A131929 A100821 this_sequence A073070 A099104 
               A066829
%Y A139689 Adjacent sequences: A139686 A139687 A139688 this_sequence A139690 A139691 
               A139692
%K A139689 nonn
%O A139689 1,1
%A A139689 Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 29 2008