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A294375
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Numbers k such that (16*10^k + 41)/3 is prime.
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0
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0, 1, 2, 3, 6, 7, 8, 12, 17, 272, 315, 405, 560, 728, 919, 1578, 1608, 4736, 7751, 18332, 22787, 50005, 69265, 91032, 92591, 148071, 168181
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OFFSET
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1,3
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COMMENTS
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For k > 1, numbers k such that the digit 5 followed by k-2 occurrences of the digit 3 followed by the digits 47 is prime (see Example section).
a(28) > 2*10^5.
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LINKS
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EXAMPLE
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2 is in this sequence because (16*10^2 + 41)/3 = 547 is prime.
Initial terms and associated primes:
a(1) = 0, 19;
a(2) = 1, 67;
a(3) = 2, 547;
a(4) = 3, 5347;
a(5) = 6, 5333347; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(16*10^# + 41)/3] &]
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CROSSREFS
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KEYWORD
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nonn,more,hard
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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