%I #12 May 07 2022 09:42:42
%S 1,1,2,2,2,2,2,4,6,2,2,4,6,2,8,2,2,6,2,4,4,2,2,8,10,12,2,12,4,8,2,4,4,
%T 2,8,12,18,2,24,8,4,4,2,4,24,2,2,4,6,20,8,6,2,2,8,8,4,4,2,16,30,2,12,
%U 2,24,4,2,4,4,24,2,24,36,36,20,12,4,24,2,4,2,4,2,24,4,2,8,8,8,24,24,4,4,2,8,8,6,6
%N The greatest common divisor of phi(n) and phi(sigma(n)).
%H Antti Karttunen, <a href="/A353643/b353643.txt">Table of n, a(n) for n = 1..16384</a>
%H Antti Karttunen, <a href="/A353643/a353643.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) = gcd(A000010(n), A062401(n)).
%F a(n) = gcd(A000010(n), A353636(n)) = gcd(A062401(n), A353636(n)).
%F a(n) = A000010(n) / A353644(n).
%F a(n) = A062401(n) / A353646(n).
%t a[n_] := GCD[EulerPhi[n], EulerPhi[DivisorSigma[1, n]]]; Array[a, 100] (* _Amiram Eldar_, May 06 2022 *)
%o (PARI) A353643(n) = gcd(eulerphi(sigma(n)), eulerphi(n));
%Y Cf. A000010, A000203, A062401, A353636, A353644, A353646.
%K nonn
%O 1,3
%A _Antti Karttunen_, May 06 2022