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A288824
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Numbers k such that (26*10^k + 61)/3 is prime.
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0
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0, 1, 2, 8, 10, 17, 18, 30, 37, 42, 47, 100, 286, 287, 440, 1074, 1124, 2298, 2879, 4948, 4950, 12730, 17429, 31768, 47726, 64220, 80200, 127240
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OFFSET
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1,3
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COMMENTS
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For k>1, numbers such that the digit 8 followed by k-2 occurrences of the digit 6 followed by the digits 87 is prime (see Example section).
a(29) > 2*10^5.
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LINKS
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EXAMPLE
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2 is in this sequence because (26*10^2 + 61)/3 = 887 is prime.
Initial terms and primes associated:
a(1) = 0, 29;
a(2) = 1, 107;
a(3) = 2, 887;
a(4) = 8, 866666687;
a(5) = 10, 86666666687; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(26*10^# + 61)/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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