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A032692
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Exactly 2 digits from {1,2,3,4,5,6,7,8,9} can precede a(n) to form a prime.
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1
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17, 117, 119, 123, 131, 143, 147, 157, 159, 173, 177, 191, 193, 197, 199, 201, 207, 227, 233, 239, 241, 247, 251, 261, 263, 279, 289, 291, 299, 303, 317, 321, 327, 331, 339, 341, 353, 357, 359, 363, 367, 369, 387, 407, 409, 411, 427, 429, 439, 443, 469
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OFFSET
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1,1
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LINKS
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EXAMPLE
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If a(n) = 469 then we find '3'469 and '6'469 to be primes.
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MATHEMATICA
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Select[Range[500], Count[Table[FromDigits[Join[{n}, IntegerDigits[#]]], {n, 9}], _?PrimeQ]==2&] (* Harvey P. Dale, Aug 27 2017 *)
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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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STATUS
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approved
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