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 A126261 #9 Oct 10 2019 13:54:42
%S A126261 1,3,11,7,137,5,363,49,19,37,83711,7,1145993,167,19,1321,42142223,65,
%T A126261 275295799,19,43,2887,444316699,133,127,1177,18469,85,9227046511387,
%U A126261 23,290774257297357,3877999,212,22737,971,229,2040798836801833,233731,1039
%N A126261 a(n) is the numerator 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 A126261 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) = 5 is the numerator of 1 +1/2 +1/6 = 5/3.
%t A126261 f[n_] := Select[Range[n], GCD[ #, n] == 1 &];g[n_] := Plus @@ (1/# &) /@ Select[Range[n], Times @@ GCD[f[ # ], n] == 1 &];Table[Numerator[g[n]], {n, 40}] (* _Ray Chandler_, Dec 24 2006 *)
%Y A126261 Cf. A126260, A126262.
%K A126261 frac,nonn
%O A126261 1,2
%A A126261 _Leroy Quet_, Dec 22 2006
%E A126261 Extended by _Ray Chandler_, Dec 24 2006