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A103016
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Numbers n such that 5*10^n + 4*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, 3, 4, 6, 10, 21, 30, 72, 199, 208, 270, 396, 619, 759, 1077, 1383, 1566, 1960, 2653, 3504, 3786, 6085, 13110
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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 (49*10^n+41)/9 is prime.
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LINKS
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Table of n, a(n) for n=1..23.
Makoto Kamada, Factorizations of 544...449.
Index entries for primes involving repunits.
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MATHEMATICA
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Do[ If[ PrimeQ[(49*10^n + 41)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A018908 A052548 A103049 * A061032 A091424 A092839
Adjacent sequences: A103013 A103014 A103015 * A103017 A103018 A103019
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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 18 2005
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EXTENSIONS
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Addition of a(23) from Kamada data by Robert Price, Dec 09 2010
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STATUS
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approved
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