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A103105
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Numbers n such that 9*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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2, 4, 41, 53, 64, 197, 238, 784, 3914, 4436, 12538, 19036
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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 (88*10^n-61)/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 977...771.
Index entries for primes involving repunits.
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MATHEMATICA
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Do[ If[ PrimeQ[(88*10^n - 61)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A012596 A012676 A184245 * A018312 A009547 A215921
Adjacent sequences: A103102 A103103 A103104 * A103106 A103107 A103108
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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(11)-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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