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 A225679 #24 Nov 21 2022 09:39:08
%S A225679 1,1,2,4,1,6,2,10,12,3,8,16,18,4,5,22,6,28,4,30,20,8,24,36,9,8,40,2,
%T A225679 42,11,46,32,52,8,12,14,58,60,15,48,10,66,44,12,70,72,18,60,4,78,20,
%U A225679 82,64,21,56,88,72,20,23,72,96,100,16,102,16,26,106,108,4
%N A225679 Numerators of phi(k)/k, as k runs through the squarefree numbers (A005117).
%C A225679 To every fraction taken by the arithmetical function m -> phi(m)/m there is exactly one n such that a(n)/A225680(n) is equal to it.
%H A225679 Amiram Eldar, <a href="/A225679/b225679.txt">Table of n, a(n) for n = 1..10000</a>
%F A225679 a(n) = A000010(A005117(n))/gcd(A000010(A005117(n)),A005117(n)).
%F A225679 Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k)/A225680(k) = Product_{p prime} (1 - 1/(p*(p+1))) = 0.7044422... (A065463). - _Amiram Eldar_, Nov 21 2022
%e A225679 A005117(5) = 6, phi(6)/6 = 2/6 = 1/3, so a(5) = 1.
%t A225679 s = Select[Range[200], SquareFreeQ]; Numerator[EulerPhi[s]/s] (* _T. D. Noe_, May 13 2013 *)
%o A225679 (PARI) lista(nn) = apply(x->(numerator(eulerphi(x)/x)), Vec(select(issquarefree, [1..nn], 1))); \\ _Michel Marcus_, Feb 22 2021
%Y A225679 Cf. A000010, A005117, A065463, A225680 (denominators).
%K A225679 nonn,frac,easy
%O A225679 1,3
%A A225679 _Franz Vrabec_, May 12 2013