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A103107
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Numbers n such that 9*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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6, 9, 90, 111, 210, 237, 414, 1192, 1260, 5836, 6772, 24861
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OFFSET
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1,1
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COMMENTS
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Also numbers n such that (89*10^n-71)/9 is prime.
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LINKS
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Table of n, a(n) for n=1..12.
Makoto Kamada, Factorizations of 988...881.
Index entries for primes involving repunits.
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MATHEMATICA
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Do[ If[ PrimeQ[(89*10^n - 71)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A046498 A119738 A204383 * A121233 A156180 A191011
Adjacent sequences: A103104 A103105 A103106 * A103108 A103109 A103110
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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(12) from Kamada data by Robert Price, Dec 14 2010
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STATUS
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approved
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