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A059764
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Initial (unsafe) primes of Cunningham chains of first type with length exactly 5. Primes in A059453 which survive as primes just four "2p+1 iterations", forming chains of exactly 5 terms.
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12
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2, 53639, 53849, 61409, 66749, 143609, 167729, 186149, 206369, 268049, 296099, 340919, 422069, 446609, 539009, 594449, 607319, 658349, 671249, 725009, 775949, 812849, 819509, 926669, 1008209, 1092089, 1132949, 1271849
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Chris Caldwell's Prime Glossary, Cunningham chains.
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FORMULA
| {(p-1)/2, p, 2p+1, 4p+3, 8p+7, 16p+15, 32p+31} = {nonprime, prime, prime, prime, prime, prime, composite}
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EXAMPLE
| 2 is here because (2-1)/2=1/2 and 32*2+31=95 are not primes, while 2,5,11,23,47 gives a first-kind-Cu5-chain of 5 primes which cannot be continued.
53639 is here because through <2p+1>, 53639 -> 107279 -> 214559 -> 429119 -> 858239 and the chain ends here (with this operator).
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CROSSREFS
| Cf. A023272, A023302, A023330, A005384, A005385, A059452-A059455, A007700, A059759, A059760, A059761, A059762, A059763, A059764, A059765, A038397, A104349, A091314, A069362, A016093, A014937, A057326.
Sequence in context: A157959 A094213 A153924 * A052427 A051833 A060895
Adjacent sequences: A059761 A059762 A059763 * A059765 A059766 A059767
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Feb 20 2001
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EXTENSIONS
| Definition corrected by Alexandre Wajnberg (alexandre.wajnberg(AT)ulb.ac.be), Aug 31 2005
Entry revised by N. J. A. Sloane (njas(AT)research.att.com), Apr 01 2006
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