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A294634
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Numbers k such that (754*10^k - 7)/9 is prime.
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0
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0, 2, 3, 5, 6, 9, 30, 38, 66, 110, 135, 168, 470, 477, 654, 1635, 1875, 2823, 12162, 23984, 32859, 33609, 34814, 39162, 58748, 82250, 161816
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OFFSET
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1,2
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COMMENTS
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Numbers such that the digits 83 followed by k occurrences of the digit 7 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 (754*10^2 - 7)/9 = 8377 is prime.
Initial terms and primes associated:
a(1) = 0, 83;
a(2) = 2, 8377;
a(3) = 3, 83777;
a(4) = 4, 8377777;
a(5) = 6, 83777777777; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(754*10^# - 7)/9] &]
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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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