A353643 The greatest common divisor of phi(n) and phi(sigma(n)).

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, 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, 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

Offset: 1

Author

Antti Karttunen, May 06 2022

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384
• Antti Karttunen, Data supplement: n, a(n) computed for n = 1..65537
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000010, A000203, A062401, A353636, A353644, A353646.

Programs

Mathematica

a[n_] := GCD[EulerPhi[n], EulerPhi[DivisorSigma[1, n]]]; Array[a, 100] (* Amiram Eldar, May 06 2022 *)

PARI

A353643(n) = gcd(eulerphi(sigma(n)), eulerphi(n));

Formula

a(n) = gcd(A000010(n), A062401(n)).

a(n) = gcd(A000010(n), A353636(n)) = gcd(A062401(n), A353636(n)).

a(n) = A000010(n) / A353644(n).

a(n) = A062401(n) / A353646(n).