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A059688
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Length of Cunningham chain containing n-th prime p(n) either as initial, internal or final term.
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2
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5, 2, 5, 2, 2, 0, 0, 0, 5, 2, 0, 0, 3, 0, 5, 2, 2, 0, 0, 0, 0, 0, 3, 6, 0, 0, 0, 2, 0, 2, 0, 2, 0, 0, 0, 0, 0, 0, 3, 2, 6, 0, 2, 0, 0, 0, 0, 0, 2, 0, 2, 2, 0, 2, 0, 2, 0, 0, 0, 2, 0, 2, 0, 0, 0, 0, 0, 0, 2, 0, 0, 6, 0, 0, 0, 2, 0, 0, 0, 0, 2, 0, 2, 0, 0, 2, 0, 0, 0, 0, 2, 2, 0, 2, 0, 2, 4, 0, 0, 0, 0, 0, 2, 0, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| The length of a chain is measured by the total number of terms including the end points. a(n)=0 means that p(n) is neither Sophie Germain nor a safe prime (i.e. it is in A059500).
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LINKS
| C. K. Caldwell, Cunningham Chains
W. Roonguthai, Yves Gallot's Proth.exe and Cunningham Chains
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EXAMPLE
| For all of {2,5,11,23,47}, i.e. at positions {j}={1,3,5,9,15} a(j)=5. Similarly for indices of all terms in {89,...,5759} a(i)=6. No chains are intelligible with length = 1 because the minimal chain enclose one SophieGermain and also one safe prime. Dominant values are 0 and 2.
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CROSSREFS
| A005384, A005385, A053176, A059452-A059456, A007700, A005602, A023272, A023302, A023330, A059500.
Sequence in context: A008566 A111129 A168464 * A073054 A072996 A153107
Adjacent sequences: A059685 A059686 A059687 * A059689 A059690 A059691
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Feb 06 2001
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