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%I #13 May 07 2022 09:42:47
%S 1,1,1,1,2,1,3,1,1,2,5,1,2,3,1,4,8,1,9,2,3,5,11,1,2,1,9,1,7,1,15,4,5,
%T 8,3,1,2,9,1,2,10,3,21,5,1,11,23,4,7,1,4,4,26,9,5,3,9,7,29,1,2,15,3,
%U 16,2,5,33,8,11,1,35,1,2,1,2,3,15,1,39,8,27,10,41,1,16,21,7,5,11,1,3,11,15,23,9,4,16,7
%N a(n) = phi(n) / gcd(phi(n), phi(sigma(n))).
%C Denominator of ratio A062401(n) / A000010(n), phi(sigma(n)) / phi(n).
%H Antti Karttunen, <a href="/A353644/b353644.txt">Table of n, a(n) for n = 1..16384</a>
%H Antti Karttunen, <a href="/A353644/a353644.txt">Data supplement: n, a(n) computed for n = 1..65537</a>
%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F a(n) = A000010(n) / A353643(n) = A000010(n) / gcd(A000010(n), A062401(n)).
%t a[n_] := (phi = EulerPhi[n])/GCD[phi, EulerPhi[DivisorSigma[1, n]]]; Array[a, 100] (* _Amiram Eldar_, May 06 2022 *)
%o (PARI) A353644(n) = { my(ph=eulerphi(n)); (ph / gcd(eulerphi(sigma(n)), ph)); };
%Y Cf. A000010, A000203, A062401, A353637, A353643, A353646 (numerators).
%K nonn,frac
%O 1,5
%A _Antti Karttunen_, May 06 2022