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A102991
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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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2
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0, 1, 4, 7, 19, 34, 54, 78, 90, 213, 307, 702, 1456, 2139, 2214, 3066, 9300, 16440, 16894, 28575
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Also numbers n such that (41*10^n-23)/9 is prime.
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LINKS
| Makoto Kamada, Factorizations of 455...553.
Index entries for primes involving repunits.
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MATHEMATICA
| Do[ If[ PrimeQ[(41*10^n - 23)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
| Sequence in context: A164265 A174465 A006381 * A062306 A140167 A006130
Adjacent sequences: A102988 A102989 A102990 * A102992 A102993 A102994
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KEYWORD
| more,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 17 2005
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EXTENSIONS
| Addition of a(17)-a(19) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 10 2010
0 added by Arkadiusz Wesolowski (wesolowski(AT)aol.pl), Mar 10 2011
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