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A102968
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Numbers n such that 3*10^n + 2*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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3, 5, 9, 12, 27, 51, 53, 147, 155, 257, 519, 603, 2885, 9509, 10524, 19650
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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 (29*10^n+61)/9 is prime.
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LINKS
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Table of n, a(n) for n=1..16.
Makoto Kamada, Factorizations of 322...229.
Index entries for primes involving repunits.
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MATHEMATICA
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Do[ If[ PrimeQ[(29*10^n+61)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A059093 A084593 A161866 * A180341 A177078 A187906
Adjacent sequences: A102965 A102966 A102967 * A102969 A102970 A102971
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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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A(13) from Julien Peter Benney (jpbenney(AT)ftml.net), Jan 16 2005
A(14) from Robert G. Wilson v, Jan 17 2005
Addition of a(15)-a(16) from Kamada data by Robert Price, Dec 12 2010
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STATUS
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approved
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