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%I #13 Jul 28 2021 04:25:31
%S 2,5,7,13,20,23,26,28,29,34,35,37,41,43,44,46,47,55,61,64,65,67,68,70,
%T 76,77,79,83,85,88,89,91,92,95,101,106,110,115,118,122,124,127,131,
%U 134,137,139,140,146,148,151,155,157,158,161,164,172,173,175,176
%N Numbers k such that k prefixed by '2' and followed by '7' is prime.
%H Harvey P. Dale, <a href="/A032719/b032719.txt">Table of n, a(n) for n = 1..1000</a>
%t Select[Range[200],PrimeQ[2*10^(IntegerLength[#]+1)+10#+7]&] (* _Harvey P. Dale_, Dec 10 2016 *)
%Y Subsequence of A001651 (not divisible by 3).
%K nonn,base
%O 1,1
%A _Patrick De Geest_, May 15 1998
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