
1) Class of prime number
Found on
https://www.crosswordclues.com/clue/wieferich-prime

In number theory, a Wieferich prime is a prime number p such that p2 divides 2p − 1 − 1, therefore connecting these primes with Fermat`s little theorem, which states that every odd prime p divides 2p − 1 − 1. Wieferich primes were first described by Arthur Wieferich in 1909 in works pertaining to Fermat`s last theorem, at which time both.....
Found on
http://en.wikipedia.org/wiki/Wieferich_prime
No exact match found.