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A032720
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Integers that when prefixed by '3' and followed by '7' yield a prime.
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0
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0, 1, 3, 4, 6, 9, 13, 16, 18, 21, 25, 30, 34, 40, 45, 46, 51, 52, 54, 55, 60, 61, 63, 67, 69, 72, 76, 79, 84, 87, 90, 91, 94, 96, 114, 117, 123, 124, 126, 127, 130, 132, 133, 135, 138, 139, 147, 151, 154, 156, 160, 162, 165, 166, 168, 172, 181, 184, 190, 195
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OFFSET
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1,3
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LINKS
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MAPLE
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q:= k-> isprime(parse(""||3||k||7)):
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MATHEMATICA
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Select[Range[0, 250], PrimeQ[FromDigits[Join[{3}, IntegerDigits[#], {7}]]]&] (* Harvey P. Dale, Dec 19 2010 *)
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PROG
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(PARI) isok(k) = isprime(eval(concat(3, concat(Str(k), 7)))); \\ Michel Marcus, Jul 16 2022
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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