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 A326531 #9 May 10 2021 01:01:42
%S A326531 0,0,0,0,0,0,0,0,0,1,1,3,4,8,10,18,22,36,45,70,86,124,148,207,252,334,
%T A326531 396,520,609,781,907,1144,1321,1653,1906,2344,2687,3278,3746,4533,
%U A326531 5143,6175,6983,8305,9337,11037,12362,14493,16168,18831,20956,24264,26876
%N A326531 Sum of the second largest parts of the partitions of n into 9 squarefree parts.
%H A326531 <a href="/index/Par#part">Index entries for sequences related to partitions</a>
%F A326531 a(n) = Sum_{q=1..floor(n/9)} Sum_{p=q..floor((n-q)/8)} Sum_{o=p..floor((n-p-q)/7)} Sum_{m=o..floor((n-o-p-q)/6)} Sum_{l=m..floor((n-m-o-p-q)/5)} Sum_{k=l..floor((n-l-m-o-p-q)/4)} Sum_{j=k..floor((n-k-l-m-o-p-q)/3)} Sum_{i=j..floor((n-j-k-l-m-o-p-q)/2)} mu(q)^2 * mu(p)^2 * mu(o)^2 * mu(m)^2 * mu(l)^2 * mu(k)^2 * mu(j)^2 * mu(i)^2 * mu(n-i-j-k-l-m-o-p-q)^2 * i, where mu is the Möbius function (A008683).
%F A326531 a(n) = A326523(n) - A326524(n) - A326525(n) - A326526(n) - A326527(n) - A326528(n) - A326529(n) - A326530(n) - A326532(n).
%t A326531 Join[{0},Table[Total[Select[IntegerPartitions[n,{9}],AllTrue[#,SquareFreeQ] &][[All,2]]],{n,60}]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jan 08 2020 *)
%Y A326531 Cf. A008683, A326522, A326523, A326524, A326525, A326526, A326527, A326528, A326529, A326530, A326532.
%K A326531 nonn
%O A326531 0,12
%A A326531 _Wesley Ivan Hurt_, Jul 11 2019