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A103063
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Numbers n such that 7*10^n + 6*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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1, 2, 6, 25, 69, 253, 300, 384, 434, 721, 822, 883, 2192, 2649, 3441, 3445, 8028, 11655
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OFFSET
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1,2
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COMMENTS
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Also numbers n such that (23*10^n-17)/3 is prime.
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LINKS
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Table of n, a(n) for n=1..18.
Makoto Kamada, Factorizations of 766...661.
Index entries for primes involving repunits.
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MATHEMATICA
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Do[ If[ PrimeQ[(23*10^n - 17)/3], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A086591 A173609 A073545 * A220191 A030228 A066317
Adjacent sequences: A103060 A103061 A103062 * A103064 A103065 A103066
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KEYWORD
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more,nonn
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AUTHOR
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Robert G. Wilson v, Jan 19 2005
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EXTENSIONS
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a(18) from Kamada data by Robert Price, Dec 14 2010
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STATUS
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approved
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