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Search: id:A056718
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| A056718 |
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Numbers n such that (61*10^n-7)/9 is prime. |
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+0
2
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| 1, 2, 4, 10, 13, 25, 115, 179, 181, 238, 785, 799, 1193, 1730, 1811, 1871, 2116, 2180, 17878, 22093
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Or, numbers n such that 6*10^n + 7*R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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LINKS
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Makoto Kamada, Factorizations of 677...77
Maksym Voznyy, Primo certificate for 2116
Maksym Voznyy, Primo certificate for 2180
Index entries for primes involving repunits
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MATHEMATICA
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Do[ If[ PrimeQ[ 6*10^n + 7*(10^n-1)/9], Print[n]], {n, 0, 5000}]
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CROSSREFS
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Sequence in context: A100912 A026224 A034233 this_sequence A057283 A082230 A107992
Adjacent sequences: A056715 A056716 A056717 this_sequence A056719 A056720 A056721
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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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The PRP's corresponding to 2116 and 2180 have been proved to be prime by Maksym Voznyy (mvoznyy0526(AT)rogers.com), Jan 05 2008, who has has found 2 new PRP's, 17878 and 22093.
Definition corrected by njas, Jan 05 2008
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