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A102498
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Values of n for which the concatenation 3nn3 (from sequence A100896) are primes.
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4
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13, 23, 28, 29, 38, 43, 49, 50, 52, 56, 64, 67, 80, 83, 92, 94, 95, 97, 1000, 1003, 1024, 1025, 1028, 1039, 1046, 1048, 1051, 1058, 1063, 1072, 1073, 1075, 1084, 1087, 1091, 1096, 1103, 1109, 1114, 1117, 1130, 1136, 1145, 1154, 1168, 1189, 1192
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OFFSET
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0,1
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LINKS
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EXAMPLE
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The number 313133 is prime and corresponds to n=13.
The number 3100010003 is prime and corresponds to n=1000.
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MATHEMATICA
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Select[Range[1200], PrimeQ[FromDigits[Join[{3}, IntegerDigits[#], IntegerDigits[ #], {3}]]]&] (* Harvey P. Dale, Dec 24 2012 *)
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CROSSREFS
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The full sequence of integers of the form 3nn3 is A100896. The primes the correspond to these values of n are sequence A102499.
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KEYWORD
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easy,nonn,base
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AUTHOR
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Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 13 2005
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STATUS
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approved
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