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 A197113 #10 Mar 30 2012 18:35:59
%S A197113 1,9,10,15,21,25,26,27,33,34,35,39,45,49,50,51,55,57,58,63,65,69,74,
%T A197113 75,77,81,82,85,87,91,93,95,99,105,106,111,115,117,119,121,122,123,
%U A197113 125,129,130,133,135,141,143,145,146,147,153,155,159,161,165,169,170
%N A197113 Nonprime numbers n such that the greatest residue of the congruence x^n (mod n) equals n-1 where x = 0..n-1.
%C A197113 Subset of A196499.
%C A197113 For all primes n, the greatest residue of the congruence x^n (mod n) where x = 0..n-1 equals n-1.
%e A197113 50 is in the sequence because the residues of the congruence x^50 (mod 50) are { 0, 1, 24, 25, 26, 49} and the greatest value is 50 - 1 = 49.
%p A197113 with(numtheory):T:=array(1..170): for n from 1 to 170 do:for k from 1 to n do:T[k]:=irem(k^n,n):od:W:=convert(T,set):x:=nops(W):if type(n,prime) = false and W[x]= n-1 then printf(`%d, `,n):else fi:od:
%Y A197113 Cf. A196499, A196082.
%K A197113 nonn
%O A197113 1,2
%A A197113 _Michel Lagneau_, Oct 13 2011