A255206 - OEIS

%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 Fröhlich_, Feb 17 2015