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 A340142 #8 Dec 29 2020 20:38:17
%S A340142 1,-1,-1,-1,-1,0,-1,-1,-2,-2,-1,1,-1,-4,-2,-1,-1,1,-1,1,-1,-8,-1,2,-4,
%T A340142 -10,-4,9,-1,6,-1,-1,-3,-14,-10,3,-1,-16,-10,4,-1,4,-1,1,5,-20,-1,3,
%U A340142 -6,-5,-14,17,-1,4,-18,-10,-7,-26,-1,8,-1,-28,-9,-1,-1,24,-1,1,-9,30,-1,4,-1,-34,-5,25,-13,22,-1,7,-8,-38,-1,-5
%N A340142 Dirichlet inverse of A160595, where A160595(x) = phi(x)/gcd(phi(x), x-1).
%H A340142 Antti Karttunen, <a href="/A340142/b340142.txt">Table of n, a(n) for n = 1..8191</a>
%H A340142 Antti Karttunen, <a href="/A340142/a340142.txt">Data supplement: n, a(n) computed for n = 1..65537</a>
%o A340142 (PARI)
%o A340142 up_to = 65537;
%o A340142 A160595(n) = { my(x=eulerphi(n)); x/gcd(x,n-1); };
%o A340142 DirInverse(v) = { my(u=vector(#v)); u[1] = (1/v[1]); for(n=2, #v, u[n] = -sumdiv(n, d, if(d<n, v[n/d]*u[d], 0))); (u) }; \\ Compute the Dirichlet inverse of the sequence given in input vector v.
%o A340142 v340142 = DirInverse(vector(up_to, n, A160595(n)));
%o A340142 A340142(n) = v340142[n];
%Y A340142 Cf. A160595.
%Y A340142 Cf. also A340141, A340143.
%K A340142 sign
%O A340142 1,9
%A A340142 _Antti Karttunen_, Dec 29 2020