The OEIS is supported by the many generous donors to the OEIS Foundation.

Primes p for which exactly three bases b with 1 < b < p exist such that p is a base b Wieferich prime.

8

`%I #8 Mar 07 2015 15:33:28
`

`%S 269,331,571,863,883,907,1097,1103,1291,1579,1697,1741,2179,2213,2221,
`

`%T 2281,2309,2311,2551,2671,2677,2693,2707,2789,2791,3191,3253,3571,
`

`%U 3617,3877,3931,4049,4787,4813,4987,5021,5153,5197,5227,5347,5519,5669,5689,5693
`

`%N Primes p for which exactly three bases b with 1 < b < p exist such that p is a base b Wieferich prime.
`

`%C p = prime(n) such that A242830(n) = 3.
`

`%o (PARI) forprime(p=1, , b=2; i=0; while(b < p, if(Mod(b, p^2)^(p-1)==1, i++); b++); if(i==3, print1(p, ", ")))
`

`%Y Cf. A255203, A255204, A255205, A255207, A255208, A255209, A255210.
`

`%K nonn
`

`%O 1,1
`

`%A _Felix FrÃ¶hlich_, Feb 17 2015
`