This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A255205 #8 Mar 07 2015 15:33:17 %S A255205 11,71,127,131,163,211,229,313,347,349,353,359,367,463,509,599,607, %T A255205 631,647,673,797,827,829,977,1021,1061,1087,1109,1123,1187,1327,1381, %U A255205 1399,1429,1453,1483,1493,1499,1523,1531,1549,1553,1607,1613,1619,1621,1657,1669 %N A255205 Primes p for which exactly two bases b with 1 < b < p exist such that p is a base b Wieferich prime. %C A255205 p = prime(n) such that A242830(n) = 2. %o A255205 (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 A255205 Cf. A255203, A255204, A255206, A255207, A255208, A255209, A255210. %K A255205 nonn %O A255205 1,1 %A A255205 _Felix Fröhlich_, Feb 17 2015