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Search: id:A056717
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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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+0
2
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| 1, 5, 7, 25, 31, 112, 199, 533, 616, 718, 787, 1357, 2779, 3889, 4192, 7537, 7945
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Also numbers n such that (55*10^n-1)/9 is prime.
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LINKS
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Makoto Kamada, Factorizations of 611...11
Index entries for primes involving repunits
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MATHEMATICA
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Do[ If[ PrimeQ[ 6*10^n + (10^n-1)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A025108 A166660 A037374 this_sequence A072370 A057490 A057253
Adjacent sequences: A056714 A056715 A056716 this_sequence A056718 A056719 A056720
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KEYWORD
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hard,nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 11 2000
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EXTENSIONS
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2779,3889,4192,7537,7945 from Hugo Pfoertner (hugo(AT)pfoertner.org), Oct 19 2004
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