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Search: id:A057175
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| A057175 |
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Numbers n such that (9^n + 1)/10 is a prime. |
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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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Repunit primes in base -9. - Paul Bourdelais (paul.bourdelais(AT)gd-ais.com)
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LINKS
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H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
Eric Weisstein's World of Mathematics, Repunit
H. Lifchitz, Mersenne and Fermat primes field
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MATHEMATICA
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lst={}; Do[p=(9^n+1)/10; If[PrimeQ[p], AppendTo[lst, n]], {n, 7!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Sep 29 2008]
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CROSSREFS
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Sequence in context: A155032 A107212 A002148 this_sequence A142642 A062629 A046024
Adjacent sequences: A057172 A057173 A057174 this_sequence A057176 A057177 A057178
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Sep 15 2000
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EXTENSIONS
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a(9)=49223, a probable prime, was discovered on Oct 22 2007. Trial factored to 1E11 with Fermat base 2 primality test. - Paul Bourdelais (paul.bourdelais(AT)gd-ais.com)
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