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%I #6 Dec 24 2012 14:12:01
%S 13,23,28,29,38,43,49,50,52,56,64,67,80,83,92,94,95,97,1000,1003,1024,
%T 1025,1028,1039,1046,1048,1051,1058,1063,1072,1073,1075,1084,1087,
%U 1091,1096,1103,1109,1114,1117,1130,1136,1145,1154,1168,1189,1192
%N Values of n for which the concatenation 3nn3 (from sequence A100896) are primes.
%H Harvey P. Dale, <a href="/A102498/b102498.txt">Table of n, a(n) for n = 0..1000</a>
%e The number 313133 is prime and corresponds to n=13.
%e The number 3100010003 is prime and corresponds to n=1000.
%t Select[Range[1200],PrimeQ[FromDigits[Join[{3},IntegerDigits[#], IntegerDigits[ #],{3}]]]&] (* _Harvey P. Dale_, Dec 24 2012 *)
%Y The full sequence of integers of the form 3nn3 is A100896. The primes the correspond to these values of n are sequence A102499.
%K easy,nonn,base
%O 0,1
%A Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 13 2005