Stern prime
If for a given prime number there is no smaller prime and nonzero integer such that , then is a Stern prime. These primes were first studied by Moritz Abraham Stern, in connection to a lesser known conjecture of Goldbach’s. Like other mathematicians of the time, Stern considered 1 to be a prime number. Thus his list of Stern primes read thus: 2, 17, 137, 227, 977, 1187, 1493. A century later the list has been amended to include 3 (as in A042978 of Sloane’s OEIS) but no terms larger than 1493 have been found. The larger of a twin prime
is not a Stern prime.