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Search: id:A063378
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| A063378 |
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Smallest number whose Sophie Germain degree (see A063377) is n. |
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+0
2
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| 4, 7, 3, 11, 5, 2, 89, 1122659, 19099919, 85864769, 26089808579, 665043081119, 554688278429, 4090932431513069, 95405042230542329
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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Also known as Cunningham chains of length n of the first kind.
For each positive integer n, is there some integer with Sophie Germain degree of n?
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LINKS
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Warut Roonguthai, Yves Gallot's Proth.exe and Cunningham Chains
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EXAMPLE
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Using f(x)=2x+1, 11 -> 23 -> 47 -> 95, which is composite; thus a(3)=11.
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MATHEMATICA
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NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; f[n_] := Block[{k = 2}, While[ Length[ NestWhileList[2# + 1 &, k, PrimeQ]] != n + 1, k = NextPrim[k]]; k]; Table[f[n], {n, 1, 8}]
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CROSSREFS
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Cf. A005384, A063377.
Sequence in context: A100127 A130204 A021215 this_sequence A020803 A019626 A005472
Adjacent sequences: A063375 A063376 A063377 this_sequence A063379 A063380 A063381
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KEYWORD
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hard,more,nonn
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AUTHOR
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Reiner Martin (reinermartin(AT)hotmail.com), Jul 14 2001
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EXTENSIONS
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More terms from Jud McCranie (j.mccranie(AT)comcast.net), Jul 20 2001
Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 21 2002
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