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 A240086 #18 Sep 05 2023 06:47:32
%S A240086 0,1,1,1,1,2,1,1,2,2,1,2,1,2,2,1,1,3,1,2,2,2,1,2,4,2,2,2,1,3,1,1,2,2,
%T A240086 2,3,1,2,2,2,1,3,1,2,3,2,1,2,6,5,2,2,1,3,2,2,2,2,1,3,1,2,3,1,2,3,1,2,
%U A240086 2,3,1,3,1,2,5,2,2,3,1,2,2,2,1,3,2,2,2,2,1,4,2,2,2,2,2,2,1,7,3,5,1,3,1,2,3
%N A240086 a(n) = Sum_{prime p|n} phi(gcd(p, n/p)) where phi is Euler's totient function.
%H A240086 Antti Karttunen, <a href="/A240086/b240086.txt">Table of n, a(n) for n = 1..10000</a>
%F A240086 If n = p^2 for some prime p then a(n) = p - 1 and a(k) <= a(n) for k <= n. - _Peter Luschny_, Sep 05 2023
%p A240086 with(numtheory): a := n -> add(phi(igcd(d, n/d)), d = factorset(n)); seq(a(n), n=1..100);
%t A240086 a[n_] := Sum[EulerPhi[GCD[p, n/p]], {p, FactorInteger[n][[;;, 1]]}]; a[1] = 0; Array[a, 100] (* _Amiram Eldar_, Aug 29 2023 *)
%o A240086 (PARI) A240086(n) = sumdiv(n,p,(isprime(p)*eulerphi(gcd(p, n/p)))); \\ _Antti Karttunen_, Sep 23 2017
%Y A240086 Cf. A000010, A001616, A010051, A001248, A006093.
%K A240086 nonn,easy
%O A240086 1,6
%A A240086 _Peter Luschny_, Mar 31 2014
%E A240086 More terms from _Antti Karttunen_, Sep 23 2017