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 A358061 #18 Oct 30 2022 03:52:45 %S A358061 0,1,0,2,0,2,0,0,0,0,0,4,0,2,0,3,0,0,0,2,0,2,0,0,2,0,2,0,0,0,0,4,0,0, %T A358061 0,3,0,2,0,0,0,4,0,2,0,2,0,6,0,2,0,0,0,2,0,0,0,0,0,4,0,2,0,4,0,4,0,2, %U A358061 0,0,0,0,0,0,4,0,0,0,0,2,4,0,0,0,0,2,0,0,0,0 %N A358061 a(n) = phi(n) mod tau(n). %C A358061 a(n) > 0 for n in A015733, a(n) = 0 for n in A020491. %F A358061 a(n) = A000010(n) mod A000005(n). %e A358061 For n = 4; a(4) = A000010(4) mod A000005(4) = 2 mod 3 = 2. %t A358061 a[n_] := Mod[EulerPhi[n], DivisorSigma[0, n]]; Array[a, 100] (* _Amiram Eldar_, Oct 28 2022 *) %o A358061 (Python) %o A358061 from math import prod %o A358061 from sympy import factorint %o A358061 def A358061(n): %o A358061 f = factorint(n).items() %o A358061 d = prod(e+1 for p, e in f) %o A358061 return prod(pow(p,e-1,d)*((p-1)%d) for p, e in f) % d # _Chai Wah Wu_, Oct 29 2022 %Y A358061 Cf. A000005 (tau), A000010 (phi), A015733, A020491. %K A358061 nonn %O A358061 1,4 %A A358061 _Ctibor O. Zizka_, Oct 28 2022