What is "cunningham chain"

n. 1 (context math English) A certain kind of sequence of prime numbers, with applications in cryptography. 2 # A ''Cunningham chain of the first kind'' of length ''n'' is a sequence of prime numbers (''p''₁, ..., ''p''_''n'') such that for all 1 ≤ ''i'' < ''n'', ''p''_''i''+1 = 2''p''_''i'' + 1. 3 # A ''Cunningham chain of the second kind'' of length ''n'' is a sequence of prime numbers (''p''₁,...,''p''_''n'') such that for all 1 ≤ ''i'' < ''n'', ''p''_''i''+1 = 2''p''_''i'' − 1.

In mathematics, a Cunningham chain is a certain sequence of prime numbers. Cunningham chains are named after mathematician A. J. C. Cunningham. They are also called chains of nearly doubled primes.