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 A341635 #17 Feb 19 2021 08:33:42
%S A341635 1,-2,-3,1,-5,6,-7,0,2,10,-11,-3,-13,14,15,0,-17,-4,-19,-5,21,22,-23,
%T A341635 0,4,26,0,-7,-29,-30,-31,0,33,34,35,2,-37,38,39,0,-41,-42,-43,-11,-10,
%U A341635 46,-47,0,6,-8,51,-13,-53,0,55,0,57,58,-59,15,-61,62,-14,0,65
%N A341635 a(n) = Sum_{d|n} phi(d) * mu(d) * mu(n/d).
%C A341635 Dirichlet inverse of A003967.
%C A341635 Moebius transform of A097945.
%C A341635 From _Vaclav Kotesovec_, Feb 19 2021: (Start)
%C A341635 Abs(a(n)) <= n.
%C A341635 a(n) = n iff n is in A030229. (End)
%H A341635 Amiram Eldar, <a href="/A341635/b341635.txt">Table of n, a(n) for n = 1..10000</a>
%F A341635 a(n) = Sum_{k=1..n} mu(gcd(n,k)) * mu(n/gcd(n,k)).
%F A341635 a(1) = 1; a(n) = -Sum_{d|n, d < n} A003967(n/d) * a(d).
%F A341635 a(n) = Sum_{d|n} mu(n/d) * A097945(d).
%F A341635 Multiplicative with a(p^e) = -p if e=1, p-1 if e=2, and 0 otherwise. - _Amiram Eldar_, Feb 19 2021
%t A341635 Table[Sum[EulerPhi[d] MoebiusMu[d] MoebiusMu[n/d], {d, Divisors[n]}], {n, 65}]
%t A341635 Table[Sum[MoebiusMu[GCD[n, k]] MoebiusMu[n/GCD[n, k]], {k, n}], {n, 65}]
%o A341635 (PARI) a(n) = sumdiv(n, d, eulerphi(d)*moebius(d)*moebius(n/d)); \\ _Michel Marcus_, Feb 17 2021
%Y A341635 Cf. A000010, A003967, A007427, A007431, A008683, A030229 (fixed points), A046099 (positions of 0's), A068341, A097945, A276833.
%K A341635 sign,mult
%O A341635 1,2
%A A341635 _Ilya Gutkovskiy_, Feb 16 2021