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%I #8 Mar 07 2015 15:33:17
%S 11,71,127,131,163,211,229,313,347,349,353,359,367,463,509,599,607,
%T 631,647,673,797,827,829,977,1021,1061,1087,1109,1123,1187,1327,1381,
%U 1399,1429,1453,1483,1493,1499,1523,1531,1549,1553,1607,1613,1619,1621,1657,1669
%N Primes p for which exactly two bases b with 1 < b < p exist such that p is a base b Wieferich prime.
%C p = prime(n) such that A242830(n) = 2.
%o (PARI) forprime(p=1, , b=2; i=0; while(b < p, if(Mod(b, p^2)^(p-1)==1, i++); b++); if(i==2, print1(p, ", ")))
%Y Cf. A255203, A255204, A255206, A255207, A255208, A255209, A255210.
%K nonn
%O 1,1
%A _Felix Fröhlich_, Feb 17 2015
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