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 A126578 #10 Oct 10 2019 13:45:44
%S A126578 1,3,4,105,4,85085,40,45045,40040,66927861,2520,167133741775,27720,
%T A126578 644658718275,16997552,4512611027925,240240,190103424450275260925,
%U A126578 816816,3873805630307495883,28269478608800,1257729100749186975,15519504
%N A126578 a(n) = denominator of the sum of reciprocals of the terms in n-th row of triangle A077581.
%e A126578 Row 4 of triangle A077581 is (1,3,5,7).
%e A126578 So a(4) is the denominator of 1/1 +1/3 +1/5 + 1/7 = 176/105.
%t A126578 row[n_] := Take[Select[Range[n^2], GCD[ #, n] == 1 &], n]; Table[Denominator[Plus @@ (1/# &) /@ row[n]], {n, 23}] (* _Ray Chandler_, Dec 29 2006 *)
%Y A126578 Cf. A077581, A126577.
%K A126578 frac,nonn
%O A126578 1,2
%A A126578 _Leroy Quet_, Dec 28 2006
%E A126578 Extended by _Ray Chandler_, Dec 29 2006