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A102972
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Numbers n such that 3*10^n + 5*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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0, 1, 3, 6, 12, 33, 69, 111, 1965, 5646, 7404, 11103, 20790, 24840
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OFFSET
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1,3
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COMMENTS
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Also numbers n such that (32*10^n+13)/9 is prime.
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LINKS
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Table of n, a(n) for n=1..14.
Makoto Kamada, Factorizations of 355...557.
Index entries for primes involving repunits.
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MATHEMATICA
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Do[ If[ PrimeQ[(32*10^n+13)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A026079 A066710 A033648 * A075209 A075207 A208131
Adjacent sequences: A102969 A102970 A102971 * A102973 A102974 A102975
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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 17 2004
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EXTENSIONS
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Addition of a(12)-a(14) from Kamada data by Robert Price, Dec 13 2010
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STATUS
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approved
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