Periodic primes: primes p whose decimal expansion can be written as sss...st, where s is nonempty string of digits not beginning with 0, there are at least two copies of s, and t (which may be absent) is a prefix of s.

A232066

Periodic primes: primes p whose decimal expansion can be written as sss...st, where s is nonempty string of digits not beginning with 0, there are at least two copies of s, and t (which may be absent) is a prefix of s.