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 A340143 #10 Dec 29 2020 20:38:23 %S A340143 1,0,0,1,0,1,0,2,2,3,0,1,0,5,3,4,0,2,0,3,2,9,0,2,4,11,6,-3,0,0,0,8,4, %T A340143 15,11,4,0,17,11,6,0,3,0,9,0,21,0,4,6,12,15,-5,0,6,19,18,8,27,0,3,0, %U A340143 29,13,16,2,-11,0,15,10,-12,0,8,0,35,12,-7,14,0,0,12,18,39,0,13,15,41,27,18,0,12,3,21,14,45,35 %N A340143 Möbius transform of A160595, where A160595(x) = phi(x)/gcd(phi(x), x-1). %H A340143 Antti Karttunen, <a href="/A340143/b340143.txt">Table of n, a(n) for n = 1..8191</a> %H A340143 Antti Karttunen, <a href="/A340143/a340143.txt">Data supplement: n, a(n) computed for n = 1..65537</a> %F A340143 a(n) = Sum_{d|n} A008683(n/d) * A160595(d). %t A340143 Table[DivisorSum[n, MoebiusMu[n/#1]*#2/GCD[#2, #3] & @@ {#, EulerPhi[#], # - 1} &], {n, 95}] (* _Michael De Vlieger_, Dec 29 2020 *) %o A340143 (PARI) %o A340143 A160595(n) = { my(x=eulerphi(n)); x/gcd(x,n-1); }; %o A340143 A340143(n) = sumdiv(n,d,moebius(n/d)*A160595(d)); %Y A340143 Cf. A008683, A160595. %Y A340143 Cf. also A340141, A340142. %K A340143 sign %O A340143 1,8 %A A340143 _Antti Karttunen_, Dec 29 2020