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A272830
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Numbers k such that (8*10^k - 29)/3 is prime.
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0
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1, 2, 3, 8, 9, 10, 16, 31, 35, 79, 179, 196, 239, 376, 515, 728, 812, 1154, 2000, 2379, 2485, 3523, 3987, 5221, 5257, 5739, 17863, 59127, 106454, 125894
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OFFSET
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1,2
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COMMENTS
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For n>1, numbers n such that the digit 2 followed by n-2 occurrences of the digit 6 followed by the digits 57 is prime (see Example section).
a(31) > 2*10^5.
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LINKS
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EXAMPLE
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3 is in this sequence because (8*10^3 - 29)/3 = 2657 is prime.
Initial terms and primes associated:
a(1) = 1, 17;
a(2) = 2, 257;
a(3) = 3, 2657;
a(4) = 8, 266666657;
a(5) = 9, 2666666657, etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(8*10^# - 29)/3] &]
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PROG
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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