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 A124676 #9 Sep 27 2019 12:39:11
%S A124676 1,2,2,4,2,6,6,6,4,10,6,12,6,3,14,16,12,18,10,6,10,22,18,20,12,24,14,
%T A124676 28,2,30,30,9,16,5,30,36,18,12,30,40,6,42,22,30,22,46,42,42,40,15,26,
%U A124676 52,48,10,42,18,28,58,30,60,30,42,62,10,6,66,34,21,4,70,66,72,36,60,38,7,12
%N A124676 a(n) = largest integer < n such that the positive integers <= a(n) and coprime to a(n) are also coprime to n.
%e A124676 The positive integers k, k <= 6, where the positive integers <= k and coprime to k are also coprime to 6, are 1,2,6. So a(6) = the largest of these < 6, which is 2.
%t A124676 f[n_] := Select[Range[n], GCD[ #, n] == 1 &];g[n_] := Select[Range[n - 1], Times @@ GCD[f[ # ], n] == 1 &];Max /@ Table[g[n], {n, 2, 80}] (* Ray Chandler, Dec 24 2006 *)
%Y A124676 Cf. A126260, A073353.
%K A124676 nonn
%O A124676 2,2
%A A124676 _Leroy Quet_, Dec 24 2006
%E A124676 Extended by _Ray Chandler_, Dec 24 2006