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Search: id:A128509
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| A128509 |
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Initial prime, greater than 7, of a prime chain of length n under the iteration x->2x-7. |
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+0
2
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| 11, 13, 13, 367, 4987, 9697, 78007, 13356127, 13356127, 6753069187, 218617084627, 35679817649197, 92975416840027
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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From the definition we see that the sequence is monotonic (but not strictly) increasing. The sequence is a generalized Cunningham chain. - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), May 12 2007
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EXAMPLE
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a(2) = 13 because 13, 13*2-7=19 and 19*2-7=31 are primes.
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MATHEMATICA
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k = 5; For[n = 2, n <= 10, n++, While[Union[PrimeQ[NestList[2# - 7 &, Prime[k], n]], PrimeQ[NestList[2# - 7 &, Prime[k], n]]] != {True}, k++ ]; Print[Prime[k]]] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), May 12 2007
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CROSSREFS
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Cf. A057330, A084954.
Sequence in context: A052258 A036212 A087551 this_sequence A043645 A043700 A111634
Adjacent sequences: A128506 A128507 A128508 this_sequence A128510 A128511 A128512
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KEYWORD
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nonn,more
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), May 07 2007
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EXTENSIONS
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Edited by Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), May 12 2007
Edited by Don Reble (djr(AT)nk.ca), Nov 07 2007
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