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 A178812 #2 Mar 30 2012 19:00:09 %S A178812 487,51 %N A178812 (2^(p-1) - 1)/p^2 modulo prime p, if p^2 divides 2^(p-1) - 1. %C A178812 (2^(p-1) - 1)/p^2 modulo p, where p is a Wieferich prime A001220. %C A178812 (2^(p-1) - 1)/p^2 modulo p, if prime p divides the Fermat quotient (2^(p-1) - 1)/p. %C A178812 See A001220 for references, links, and additional comments. %F A178812 a(n) = (2^(p-1) - 1)/p^2 modulo p, where p = A001220(n). %F A178812 a(1) = A178813(1). %e A178812 a(1) = 487 as the first Wieferich prime is 1093 and (2^1092 - 1)/1093^2 == 487 (mod 1093). %e A178812 The 2nd Wieferich prime is 3511 and (2^3510 - 1)/3511^2 == 51 (mod 3511), so a(2) = 51. %Y A178812 Cf. A001220, A178813. %K A178812 bref,hard,more,nonn %O A178812 1,1 %A A178812 _Jonathan Sondow_, Jun 16 2010