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 A280250 #23 May 12 2025 15:31:16
%S A280250 1,3,4,6,8,14,11,17,16,32,27,39,39,58,47,61,65,93,67,95,80,130,94,142,
%T A280250 106,203,130,189,151,232,165,246,187,311,235,362,260,389,259,377,283,
%U A280250 442,306,473,367,511,407,530,395,625,458,673,493,801,507,782,548,842,590,901
%N A280250 Sum of the smaller parts of the partitions of 2n into 2 squarefree parts.
%H A280250 Harvey P. Dale, <a href="/A280250/b280250.txt">Table of n, a(n) for n = 1..1000</a>
%H A280250 <a href="/index/Par#part">Index entries for sequences related to partitions</a>
%F A280250 a(n) = Sum_{i=1..n} i * mu(i)^2 * mu(2*n-i)^2, where mu is the Möbius function (A008683).
%F A280250 a(n) = A280252(n) - A280251(n).
%p A280250 with(numtheory): A280250:=n->sum(i*mobius(i)^2*mobius(2*n-i)^2, i=1..n): seq(A280250(n), n=1..100);
%t A280250 Table[Total[Select[IntegerPartitions[2 n,{2}],AllTrue[#,SquareFreeQ]&][[;;,2]]],{n,60}] (* _Harvey P. Dale_, May 12 2025 *)
%Y A280250 Cf. A008683, A185297, A280226, A280251, A280252.
%K A280250 nonn,easy
%O A280250 1,2
%A A280250 _Wesley Ivan Hurt_, Dec 29 2016