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A269303
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Numbers k such that (266*10^k + 1)/3 is prime.
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504
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0, 1, 2, 3, 4, 5, 6, 8, 10, 13, 19, 26, 37, 69, 77, 81, 214, 242, 255, 900, 1113, 1833, 3166, 3566, 4753, 4849, 4869, 5005, 7372, 7702, 10240, 16100, 18972, 28574, 33815, 37820, 70457, 89482, 106066, 133603, 154897, 278325
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OFFSET
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1,3
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COMMENTS
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Numbers k such that digits 88 followed by k-1 occurrences of digit 6 followed by the digit 7 is prime (see Example section).
a(43) > 3*10^5.
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LINKS
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EXAMPLE
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6 is in this sequence because (266*10^n+1)/3 = 88666667 is prime.
Initial terms and primes associated:
a(1) = 0, 89;
a(2) = 1, 887;
a(3) = 2, 8867;
a(4) = 3, 88667;
a(5) = 4, 886667;
a(6) = 5, 8866667;
a(7) = 6, 88666667;
a(8) = 8, 8866666667;
a(9) = 10, 886666666667;
a(10) = 13, 886666666666667, etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(266*10^#+1)/3] &]
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PROG
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(Magma) [n: n in [0..220] | IsPrime((266*10^n + 1) div 3)]; // Vincenzo Librandi, Feb 23 2016
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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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