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 A120286 #9 May 02 2024 10:46:42
%S A120286 1,9,65,725,3899,28763,419017,864669,7981633,3586319,200763407,
%T A120286 2649665993,34899471137,176508049513,356606957297,12234391348253,
%U A120286 209672027529221,4012917216669239,15350275129353301,15443118015171841
%N A120286 Numerator of 1/n^2 + 2/(n-1)^2 + 3/(n-2)^2 +...+ (n-1)/2^2 + n.
%C A120286 p^2 divides a(p-1) for prime p>2. p divides a(p-2) for prime p>3.
%F A120286 a(n) = numerator[Sum[Sum[1/i^2,{i,1,k}],{k,1,n}]].
%t A120286 Numerator[Table[Sum[Sum[1/i^2,{i,1,k}],{k,1,n}],{n,1,30}]]
%t A120286 Table[-EulerGamma + HarmonicNumber[1 + n, 2] + n*HarmonicNumber[1 + n, 2] - PolyGamma[0, 2 + n], {n, 1, 20}] // Numerator (* _Vaclav Kotesovec_, May 02 2024 *)
%o A120286 (Python)
%o A120286 from fractions import Fraction
%o A120286 def A120286(n): return sum(Fraction(n-i+1,i**2) for i in range(1,n+1)).numerator # _Chai Wah Wu_, May 01 2024
%Y A120286 Cf. A027612, A001008, A007406, A007407, A370774 (denom.).
%K A120286 frac,nonn
%O A120286 1,2
%A A120286 _Alexander Adamchuk_, Jul 07 2006