%I #10 Jul 28 2021 04:25:39
%S 0,1,4,7,19,21,24,25,27,28,31,33,36,39,42,54,57,60,63,73,82,85,90,91,
%T 94,96,97,99,100,102,105,129,135,141,148,150,154,162,163,165,166,168,
%U 171,175,183,192,196,198,201,204,205,213,220,229,232,234,241,246,247
%N Numbers k such that k prefixed by '6' and followed by '7' is a prime.
%t Select[Range[0,300],PrimeQ[FromDigits[Join[{6},IntegerDigits[#],{7}]]]&] (* _Harvey P. Dale_, Mar 23 2015 *)
%K nonn,base
%O 1,3
%A _Patrick De Geest_, May 15 1998
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