In mathematics, a Wieferich pair is a pair of prime numbers p and q that satisfy pq ⁻ ¹ ≡ 1 and qᵖ ⁻ ¹ ≡ 1 Wieferich pairs are named after German mathematician Arthur Wieferich. Wieferich pairs play an important role in Preda Mihăilescu's 2002... Wikipedia