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A102374
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Numbers k such that k77777 is prime.
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1
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24, 32, 39, 50, 54, 66, 74, 75, 78, 83, 90, 99, 101, 108, 110, 114, 135, 143, 152, 159, 167, 173, 186, 188, 204, 206, 207, 209, 219, 221, 230, 233, 236, 242, 248, 251, 255, 261, 263, 264, 276, 279, 284, 285, 321, 338, 341, 356, 362, 372, 374, 380, 393, 401, 404, 422, 426, 428, 431, 437, 461
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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=24, then k77777 = 2477777 (prime).
If k=66, then k77777 = 6677777 (prime).
If k=99, then k77777 = 9977777 (prime).
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MATHEMATICA
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Select[Range[500], PrimeQ[#*10^5+77777]&] (* Harvey P. Dale, Sep 19 2020 *)
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PROG
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(Magma) [ n: n in [1..700] | IsPrime(Seqint([7, 7, 7, 7, 7] cat Intseq(n))) ]; // Vincenzo Librandi, Feb 04 2011
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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