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A110674
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Numbers k such that the string 1111k is prime.
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1
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3, 7, 9, 19, 21, 27, 43, 49, 87, 91, 151, 157, 169, 181, 183, 189, 211, 213, 219, 247, 259, 283, 289, 301, 333, 339, 351, 361, 379, 393, 399, 423, 427, 433, 447, 457, 489, 493, 499, 531, 543, 547, 553, 559, 573, 577, 637, 639, 651, 661, 667, 673, 687, 703, 711
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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 k=91 then 1111k = 111191 (prime).
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MATHEMATICA
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Select[Range[720], PrimeQ[1111*10^IntegerLength[#] + #] &] (* Michael De Vlieger, Jan 22 2018 *)
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PROG
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(Magma) [ n: n in [1..1750] | IsPrime(Seqint(Intseq(n) cat [1, 1, 1, 1])) ]; // Vincenzo Librandi, Feb 02 2011
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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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