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Search: id:A109828
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| A109828 |
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Smallest prime beginning a complete Cunningham chain (of the second kind) of length n. |
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+0
6
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| 11, 7, 2, 2131, 1531, 385591, 16651, 15514861, 857095381, 205528443121, 1389122693971, 216857744866621, 758083947856951
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The chain begins with a prime number p; next term p' (a prime) is produced forming 2p-1; next term p"=2p'-1, etc. "Complete" means that each chain is exactly n primes long (i.e. the chain cannot be a subchain of another one). That is why this sequence is slightly different from A005602, where the 6th term (33301) is smaller than here (385591) but is the second one of a seven primes sequence and therefore doesn't *start* a sequence.
Similarly for A064812 where some terms do not strictly *start* a chain.
According to the web site http://users.cybercity.dk/~dsl522332/math/Cunningham_Chain_records.htm, the numbers 107588900851484911, 69257563144280941, 3203000719597029781 are also in the sequence. - Dmitry Kamenetsky (dkamen(AT)rsise.anu.edu.au), May 14 2009
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LINKS
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Chris Caldwell, Cunningham chains.
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CROSSREFS
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Cf. A005602, A057331.
Sequence in context: A038320 A010185 A005603 this_sequence A048981 A132361 A155914
Adjacent sequences: A109825 A109826 A109827 this_sequence A109829 A109830 A109831
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KEYWORD
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nonn
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AUTHOR
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Alexandre Wajnberg (alexandre.wajnberg(AT)ulb.ac.be), Aug 30 2005
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