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 A178814 #2 Mar 30 2012 19:00:09 %S A178814 0,487,4,974,1,30384,1,1,0,2,46,1571,1,17,24160,855,0,4,1,189,1,5,11, %T A178814 1,0,0,1,0,1,3,2,3,0,19632919407,1,60768,1,11,1435,8,0,0,2,2,1,1 %N A178814 (n^(p-1) - 1)/p^2 mod p, where p is the first prime that divides (n^(p-1) - 1)/p. %C A178814 (n^(p-1) - 1)/p^2 mod p, where p is the first prime such that p^2 divides n^(p-1) - 1. %C A178814 See references and additional comments, links, and cross-refs in A001220 and A039951. %H A178814 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fermat_quotient#Generalized_Wieferich_primes">Generalized Wieferich primes</a> %F A178814 a(n) = (n^(p-1) - 1)/p^2 mod p, where p = A039951(n). %F A178814 a(n) = k mod 2, if n = 4k+1. %F A178814 a(prime(n)) = A178813(n). %e A178814 The first prime p that divides (3^(p-1) - 1)/p is 11, so a(3) = (3^10 - 1)/11^2 mod 11 = 488 mod 11 = 4. %Y A178814 a(2) = A178812(1) = A178813(1). Cf. A001220, A039951, A174422. %K A178814 hard,more,nonn %O A178814 1,2 %A A178814 _Jonathan Sondow_, Jun 17 2010