Pillai prime
If for a given prime we can find an integer such that but then is a called a Pillai prime. These are listed in A063980 of Sloane’s OEIS. Sarinya Intaraprasert proved that there are infinitely many Pillai primes. The first few are 23, 29, 59, 61, 67, 71, 79, 83, 109, 137, 139, 149, 193, …
References
- 1 R. K. Guy, Unsolved Problems in Number Theory
New York: Springer-Verlag 2004: A2