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 A368674 #8 Jan 03 2024 05:36:58
%S A368674 0,0,2,3,5,5,16,21,20,16,33,33,44,48,63,84,86,92,103,105,112,130,165,
%T A368674 177,183,173,211,191,214,202,273,302,290,318,359,395,406,422,465,503,
%U A368674 520,508,603,611,623,621,692,728,732,722,719,749,790,832,827,875,876,924,1013,1001
%N A368674 Sum of the squarefree numbers less than n that do not divide n.
%F A368674 a(n) = Sum_{k=1..n} k * mu(k)^2 * (ceiling(n/k) - floor(n/k)).
%e A368674 a(12) = 33. There are 4 squarefree numbers less than 12 that do not divide 12, namely: 5, 7, 10, and 11. Their sum is 5 + 7 + 10 + 11 = 33.
%t A368674 Table[Sum[k*MoebiusMu[k]^2 (Ceiling[n/k] - Floor[n/k]), {k, n}], {n, 100}]
%o A368674 (PARI) a(n) = sum(k=1, n-1, if ((n % k) && issquarefree(k), k)); \\ _Michel Marcus_, Jan 03 2024
%Y A368674 Cf. A008683 (mu), A368673.
%K A368674 nonn,easy
%O A368674 1,3
%A A368674 _Wesley Ivan Hurt_, Jan 02 2024