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 A355658 #8 Jul 17 2022 10:51:36 %S A355658 5,17,7,19,3,19,131,127,263,41,229,691,313,19,53,521,53,601,1301,11, %T A355658 619,31,269,3187,53,181,43,317,499,373,911,659,19,3659,313,751,233, %U A355658 4373,3307,419,2591,313,1249,2897,349,709,331,1973,1933,503,821,977,2371,263 %N A355658 Smallest prime base q such that q^(p-1) == 1 (mod p^2), where p = prime(n). %C A355658 a(n) differs from A125636(n) if and only if p is a Wieferich prime (A001220). In particular, a(183) = 2 and A125636(183) = 18979. Similarly, a(490) = 2 and A125636(490) = 82183. %o A355658 (PARI) a(n) = my(p=prime(n)); forprime(q=1, , if(Mod(q, p^2)^(p-1)==1, return(q))) %Y A355658 Cf. A001220, A125636, A039678. %K A355658 nonn %O A355658 1,1 %A A355658 _Felix Fröhlich_, Jul 12 2022