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A102943
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Numbers n such that 10^n + 7*R_n + 2 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, 8, 10, 25, 50, 76, 104, 4406, 8935, 26000
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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 (16*10^n+11)/9 is prime.
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LINKS
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Table of n, a(n) for n=1..11.
Makoto Kamada, Factorizations of 177...779.
Index entries for primes involving repunits.
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MATHEMATICA
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Do[ If[ PrimeQ[(16*10^n + 11)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A106358 A209449 A002510 * A062880 A066707 A107227
Adjacent sequences: A102940 A102941 A102942 * A102944 A102945 A102946
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KEYWORD
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more,nonn
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AUTHOR
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Robert G. Wilson v, Dec 16 2004
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EXTENSIONS
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Addition of a(11) from Kamada data by Robert Price, Dec 13 2010
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STATUS
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approved
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