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 A281904 #5 Feb 05 2017 13:17:17
%S A281904 1,4,9,16,31,58,93,144,221,343,502,733,1048,1495,2089,2881,3947,5357,
%T A281904 7205,9618,12758,16812,22001,28623,37037,47720,61121,77973,99029,
%U A281904 125322,157874,198205,247954,309203,384260,476116,588149,724613,890175,1090781,1333193,1625702,1977505,2400221,2906800,3513121
%N A281904 Expansion of Sum_{i>=1} mu(i)^2*i*x^i/(1 - x^i) / Product_{j>=1} (1 - x^j), where mu() is the Moebius function (A008683).
%C A281904 Total sum of squarefree parts in all partitions of n.
%C A281904 Convolution of the sequences A000041 and A048250.
%H A281904 <a href="/index/Par#partN">Index entries for related partition-counting sequences</a>
%F A281904 G.f.: Sum_{i>=1} mu(i)^2*i*x^i/(1 - x^i) / Product_{j>=1} (1 - x^j).
%e A281904 a(4) = 16 because we have [4], [3, 1], [2, 2], [2, 1, 1], [1, 1, 1, 1] and 3 + 1 + 2 + 2 + 2 + 1 + 1 + 1 + 1 + 1 + 1 = 16.
%t A281904 nmax = 46; Rest[CoefficientList[Series[Sum[MoebiusMu[i]^2 i x^i/(1 - x^i), {i, 1, nmax}] / Product[1 - x^j, {j, 1, nmax}], {x, 0, nmax}], x]]
%Y A281904 Cf. A000041, A005117, A008683, A048250, A066186, A073118.
%K A281904 nonn
%O A281904 1,2
%A A281904 _Ilya Gutkovskiy_, Feb 01 2017