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 A126262 #9 Oct 10 2019 13:54:23
%S A126262 1,2,6,4,60,3,140,24,9,20,27720,4,360360,84,10,560,12252240,36,
%T A126262 77597520,10,21,1320,118982864,72,50,520,7560,42,2329089562800,15,
%U A126262 72201776446800,1441440,99,9520,420,120,485721041551200,95760,468,24,19914562703599200
%N A126262 a(n) is the denominator of the sum of the reciprocals of the positive integers k, k<=n, where every positive integer <= k and coprime to k is also coprime to n.
%e A126262 The positive integers k, k <= 6, where every positive integer <=k and coprime to k is also coprime to 6, are 1,2,6. So a(6) = 3 is the denominator of 1 +1/2 +1/6 = 5/3.
%t A126262 f[n_] := Select[Range[n], GCD[ #, n] == 1 &];g[n_] := Plus @@ (1/# &) /@ Select[Range[n], Times @@ GCD[f[ # ], n] == 1 &];Table[Denominator[g[n]], {n, 41}] (* _Ray Chandler_, Dec 24 2006 *)
%Y A126262 Cf. A126260, A126261.
%K A126262 frac,nonn
%O A126262 1,2
%A A126262 _Leroy Quet_, Dec 22 2006
%E A126262 Extended by _Ray Chandler_, Dec 24 2006