Cunningham chain

In mathematics, a Cunningham chain is a certain sequence of prime numbers. Cunningham chains are named after mathematician A. J. C. Cunningham.

A Cunningham chain of the first kind is a sequence of prime numbers (p₁,...,p_n) such that for all 1 ≤ i < n, p_i is a Sophie Germain prime - that is, p_i+1 = 2 p_i + 1. Similarly, a Cunningham chain of the second kind is a sequence of prime numbers (p₁,...,p_n) such that for all 1 ≤ i < n, p_i+1 = 2 p_i - 1.

Cunningham chains are also sometimes generalized to sequences of prime numbers (p₁,...,p_n) such that for all 1 ≤ i < n, p_i+1 = ap_i + b for fixed relatively prime integers a, b; the resulting chains are called generalized Cunningham chains.

A Cunningham chain is called complete if it cannot be further extended, i.e., if the next term in the chain would not be a prime number anymore.

External links

• The Prime Glossary: Cunningham chain
• PrimeLinks++: Cunningham chain