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 A304575 #14 Nov 21 2024 06:06:26
%S A304575 1,2,3,4,4,6,6,8,7,8,8,12,9,12,12,15,12,16,13,17,16,18,16,24,17,20,20,
%T A304575 23,18,26,20,28,23,26,24,33,24,29,28,35,27,35,29,37,34,35,31,46,32,38,
%U A304575 35,41,33,45,36,47,38,42,37,54,38,46,46,54,42,53,42,54
%N A304575 a(n) = Sum_{d|n} #{k < d, k squarefree and relatively prime to d}.
%C A304575 Note that a(n) <= n.
%H A304575 Amiram Eldar, <a href="/A304575/b304575.txt">Table of n, a(n) for n = 1..10000</a>
%F A304575 a(n) = Sum_{d|n} A073311(d) (inverse Moebius transform of A073311). - _Amiram Eldar_, Nov 21 2024
%t A304575 s[n_]:=Length[Select[Range[n],And[SquareFreeQ[#],GCD[n,#]===1]&]];
%t A304575 Table[DivisorSum[n,s],{n,100}]
%o A304575 (PARI) a(n) = sumdiv(n, d, #select(k->(issquarefree(k) && (gcd(k, d)==1)), [1..d])); \\ _Michel Marcus_, May 15 2018
%Y A304575 Cf. A000010, A001221, A005117, A008683, A073311, A111972, A112399, A139555, A265675, A304573, A304575, A304576.
%K A304575 nonn
%O A304575 1,2
%A A304575 _Gus Wiseman_, May 14 2018