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A103015
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Numbers n such that 5*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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2, 6, 8, 18, 53, 68, 242, 276, 320, 564, 620, 1782, 2340, 2454, 5765, 15530, 15605, 22938
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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 (49*10^n+23)/9 is prime.
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LINKS
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Table of n, a(n) for n=1..18.
Makoto Kamada, Factorizations of 544...447.
Index entries for primes involving repunits.
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MATHEMATICA
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Do[ If[ PrimeQ[(49*10^n + 23)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A102656 A163911 A077638 * A098092 A221316 A106164
Adjacent sequences: A103012 A103013 A103014 * A103016 A103017 A103018
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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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a(16)-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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