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A056717
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Numbers n such that 6*10^n + R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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1, 5, 7, 25, 31, 112, 199, 533, 616, 718, 787, 1357, 2779, 3889, 4192, 7537, 7945, 23938, 32632, 49169, 56453, 61097, 90211
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Also numbers n such that (55*10^n-1)/9 is prime.
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LINKS
| Makoto Kamada, Factorizations of 611...11
Index entries for primes involving repunits
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MATHEMATICA
| Do[ If[ PrimeQ[ 6*10^n + (10^n-1)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
| Cf. A093631.
Sequence in context: A025108 A166660 A037374 * A072370 A057490 A057253
Adjacent sequences: A056714 A056715 A056716 * A056718 A056719 A056720
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KEYWORD
| nonn,changed
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 11 2000
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EXTENSIONS
| 2779,3889,4192,7537,7945 from Hugo Pfoertner (hugo(AT)pfoertner.org), Oct 19 2004
23938 from Ray Chandler (rayjchandler(AT)sbcglobal.net), Sep 25 2010
32632 and 49169 from Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 08 2012
56453 from Serge Batalov, Mar 12 2009 confirmed as next term by Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 09 2012
61097 from Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 09 2012
90211 from Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 10 2012
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