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A271506
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Numbers k such that (7*10^k + 179)/3 is prime.
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0
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1, 2, 3, 7, 8, 36, 41, 46, 74, 76, 88, 103, 115, 188, 194, 257, 310, 399, 511, 515, 776, 1134, 1404, 6545, 6569, 17600, 22209, 24397, 24842, 46957, 116684, 118607, 131339, 202267
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OFFSET
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1,2
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COMMENTS
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For k>1, numbers such that the digit 2 followed by k-2 occurrences of the digit 3 followed by the digits 93 is prime (see Example section).
a(35) > 3*10^5.
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LINKS
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EXAMPLE
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3 is in this sequence because (7*10^3 + 179)/3 = 2393 is prime.
Initial terms and primes associated:
a(1) = 1, 83;
a(2) = 2, 293;
a(3) = 3, 2393;
a(4) = 7, 23333393;
a(5) = 8, 233333393. etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(7*10^# + 179)/3] &]
Join[{1}, Flatten[Position[Table[100*FromDigits[PadRight[{2}, n, 3]]+93, {n, 47000}], _?PrimeQ]]+1] (* Harvey P. Dale, Dec 11 2018 *)
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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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