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 A120487 #6 May 18 2019 16:57:35
%S A120487 1,2,3,12,5,20,35,280,63,2520,385,27720,6435,8008,45045,720720,85085,
%T A120487 4084080,969969,739024,29393,5173168,7436429,356948592,42902475,
%U A120487 2974571600,717084225,80313433200,215656441,2329089562800,4512611027925
%N A120487 Denominator of 1^n/n + 2^n/(n-1) + 3^n/(n-2) + ... + (n-1)^n/2 + n^n/1.
%C A120487 Numerator is A115071(n).
%C A120487 Also a(n) is denominator of (n+1)^(n+1) * (H(n+1) - 1), where H(k) is harmonic number, H(k) = Sum_{i=1..k} 1/i = A001008(k)/A002805(k). - _Alexander Adamchuk_, Jan 02 2007
%F A120487 a(n) = denominator(Sum_{k=1..n} k^n/(n-k+1)).
%F A120487 a(n) = denominator((n+1)^(n+1) * Sum_{i=2..n+1} 1/i). - _Alexander Adamchuk_, Jan 02 2007
%t A120487 Denominator[Table[Sum[k^n/(n-k+1),{k,1,n}],{n,1,50}]]
%t A120487 Table[ Denominator[ (n+1)^(n+1) * Sum[ 1/i,{i,2,n+1} ] ], {n,1,40} ] (* _Alexander Adamchuk_, Jan 02 2007 *)
%Y A120487 Cf. A115071, A027612, A031971, A002805.
%Y A120487 Cf. A001008, A002805.
%K A120487 frac,nonn
%O A120487 1,2
%A A120487 _Alexander Adamchuk_, Jul 22 2006