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 A143811 #4 Mar 30 2012 17:22:50
%S A143811 1,1,1,1,3,1,1,1,1,2,1,2,1,2,1,1,2,1,1,3,1,2,1,1,2,1,2,1,2,2,3,3,2,1,
%T A143811 1,2,1,3,1,1,1,2,2,1,2,2,3,2,1,3,2,1,2,1,2,2,4,1,1,2,2,2,2,1,3,1,4,1,
%U A143811 3,3,3,3,3,2,2,1,1,2,2,1,2,2,1,2,2,1,2,1,2,3,1,1,5,1,2,1,3,2,2,1,2,2,2,1,4
%N A143811 Number of numbers k<p such that k^(p-1)-1 is divisible by p^2, p = prime(n).
%C A143811 Note that a(n)>0 because k=1 is always a solution. The primes for which a(n)>1 are given in A134307. The values of k are the terms <p in row n of A143548. The largest known terms in this sequence are for the Wieferich primes 1093 and 3511, for which we have a(183)=11 and a(490)=12, respectively. It is not hard to show that k=p-1 is never a solution for odd prime p. In fact, (p-1)^(p-1)=p+1 (mod p^2) for odd prime p.
%H A143811 T. D. Noe, <a href="/A143811/b143811.txt">Table of n, a(n) for n=1..10000</a>
%t A143811 Table[p=Prime[n]; s=Select[Range[p-1], PowerMod[ #,p-1,p^2]==1&]; Length[s], {n,100}]
%K A143811 nonn
%O A143811 1,5
%A A143811 _T. D. Noe_, Sep 02 2008