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 A309192 #9 Jul 16 2019 08:33:12
%S A309192 1,4,8,11,17,29,37,40,44,62,74,86,100,124,148,151,169,181,201,219,251,
%T A309192 287,311,323,329,371,375,399,429,501,533,536,584,638,686,698,736,796,
%U A309192 852,870,912,1008,1052,1088,1112,1184,1232,1244,1252,1270,1342,1384,1438,1450,1522
%N A309192 a(n) = Sum_{k=1..n} mu(k)^2 * k * floor(n/k).
%C A309192 Partial sums of A048250.
%H A309192 Vaclav Kotesovec, <a href="/A309192/b309192.txt">Table of n, a(n) for n = 1..10000</a>
%F A309192 G.f.: (1/(1 - x)) * Sum_{k>=1} mu(k)^2 * k * x^k/(1 - x^k).
%F A309192 a(n) ~ n^2/2. - _Vaclav Kotesovec_, Jul 16 2019
%t A309192 Table[Sum[MoebiusMu[k]^2 k Floor[n/k], {k, 1, n}], {n, 1, 55}]
%t A309192 nmax = 55; CoefficientList[Series[1/(1 - x) Sum[MoebiusMu[k]^2 k x^k/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
%t A309192 Accumulate[Table[Total[Select[Divisors[n], SquareFreeQ]], {n, 1, 100}]] (* _Vaclav Kotesovec_, Jul 16 2019 *)
%Y A309192 Cf. A008683, A024916, A024924, A048250, A064608, A275205.
%K A309192 nonn
%O A309192 1,2
%A A309192 _Ilya Gutkovskiy_, Jul 16 2019