Smallest Cunningham Chain of the First Kind of Length 6

Theorem
The smallest Cunningham chain of the first kind of length $6$ is:
 * $\tuple {89, 179, 359, 719, 1439, 2879}$

Proof
By definition, a Cunningham chain of the first kind is a sequence of prime numbers $\tuple {p_1, p_2, \ldots, p_n}$ such that:
 * $p_{k + 1} = 2 p_k + 1$
 * $\dfrac {p_1 - 1} 2$ is not prime
 * $2 p_n + 1$ is not prime.

Thus each term except the last is a Sophie Germain prime.

Let $P: \Z \to \Z$ be the mapping defined as:
 * $\map P n = 2 n + 1$

Applying $P$ iteratively to each of the smallest Sophie Germain primes in turn:

Thus $\tuple {2, 5, 11, 23, 47}$ is a Cunningham chain of the first kind of length $5$.

It is noted that $\dfrac {89 - 1} 2 = 44$ which is not prime.

Hence the sequence of $6$:
 * $\tuple {89, 179, 359, 719, 1439, 2879}$