Thread: is it possible
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Old 2020-07-08, 19:21   #10
carpetpool
 
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"Sam"
Nov 2016

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Cunningham Chain of the second kind

Quote:
Originally Posted by PrimePages
A Cunningham chain of length k (of the first kind) is sequence of k primes, each which is twice the preceding one plus one. For example, {2, 5, 11, 23, 47} and {89, 179, 359, 719, 1439, 2879}.

A Cunningham chain of length k (of the second kind) is a sequence of k primes, each which is twice the preceding one minus one. (For example, {2, 3, 5} and {1531, 3061, 6121, 12241, 24481}.)
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OP is mentioning a special case of this (k=2, Fermat Primes), there are only finitely such primes as Paul mentioned.

Last fiddled with by carpetpool on 2020-07-08 at 19:22
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