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%I #11 Nov 06 2022 07:48:04
%S 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,
%T 1,0,0,1,0,1,0,0,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,1,0,0,1,0,0,0,0,0,0,
%U 0,1,0,0,0,1,0,0,0,1,1,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,1,1,0,0,1,0,0,1,0
%N If (n-th Chen prime) + 2 is a prime then 1 else 0.
%H Reinhard Zumkeller, <a href="/A139689/b139689.txt">Table of n, a(n) for n = 1..1000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ChenPrime.html">Chen Prime</a>
%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%F a(n) = 2 - A001222(A139690(n)).
%F a(n) = A010051(A139690(n)) = 1 - A064911(A139690(n)).
%Y Cf. A001222, A010051, A064911, A139690.
%K nonn
%O 1,1
%A _Reinhard Zumkeller_, Apr 29 2008
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