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A102992
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Numbers n such that 4*10^n + 5*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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3
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1, 2, 4, 5, 13, 22, 25, 28, 38, 67, 142, 284, 295, 380, 397, 1217, 1640, 2885, 3286, 7735, 29306
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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 (41*10^n+13)/9 is prime.
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LINKS
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Table of n, a(n) for n=1..21.
Makoto Kamada, Factorizations of 455...557.
Index entries for primes involving repunits.
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MATHEMATICA
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Do[ If[ PrimeQ[(41*10^n + 13)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A139485 A079407 A078652 * A136563 A127077 A104549
Adjacent sequences: A102989 A102990 A102991 * A102993 A102994 A102995
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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 17 2005
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EXTENSIONS
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Addition of a(21)from Kamada data by Robert Price, Dec 09 2010
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STATUS
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approved
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