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Search: id:A098960
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| A098960 |
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Numbers n such that 2*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n. |
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+0
2
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OFFSET
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1,1
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COMMENT
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Also numbers n such that (25*10^n-61)/9 is prime.
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LINKS
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Makoto Kamada, Factorizations of 277...771.
Index entries for primes involving repunits.
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EXAMPLE
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For n = 2 and 6, we get 271 and 2777771 which are primes.
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MATHEMATICA
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Do[ If[ PrimeQ[(25*10^n - 61)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A013976 A083666 A083126 this_sequence A018952 A019028 A127114
Adjacent sequences: A098957 A098958 A098959 this_sequence A098961 A098962 A098963
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KEYWORD
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more,nonn
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AUTHOR
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Julien Peter Benney (jpbenney(AT)ftml.net), Oct 22 2004
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EXTENSIONS
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a(6) from Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 04 2004
a(7), a(8) & a(9) from Sam Handler (sam_5_5_5_0(AT)yahoo.com), Nov 03 2004
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