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 A264389 #13 Mar 13 2018 05:09:09
%S A264389 1,1,18,8,5,18,14,16,27,5,22,72,13,14,90,32,17,27,38,40,63,22,46,144,
%T A264389 25,13,162,56,29,90,62,64,99,17,70,216,37,38,234,80,41,63,86,88,135,
%U A264389 46,94,288,49,25,306,104,53,162,110,112,171,29,118,360,61,62,378
%N A264389 Denominator of binomial(n-1, 2)/(6*n), for n >= 1. Denominator of Dedekind sum s(1,n).
%C A264389 See A264388 for the numerators and details about the Dedekind sum s(1,n), as well as references.
%F A264389 a(n) = denominator(binomial(n-1, 2)/(6*n)), n >= 1.
%F A264389 a(n) = denominator(s(1,n)), with s(1,n) = Sum_{r=1..(n-1)} (r/n)*(r/n - floor(r/n)- 1/2), n >= 1, where s(h,k) are the Dedekind sums.
%t A264389 Denominator[Table[Binomial[n-1,2]/(6n),{n,50}]] (* _Harvey P. Dale_, Aug 30 2016 *)
%o A264389 (Julia)
%o A264389 using Nemo
%o A264389 A264389(n) = denominator(dedekind_sum(1, n))
%o A264389 [A264389(n) for n in 1:70] |> println # _Peter Luschny_, Mar 13 2018
%Y A264389 Cf. A264388.
%K A264389 nonn,easy,frac
%O A264389 1,3
%A A264389 _Wolfdieter Lang_, Jan 11 2016