A353644 a(n) = phi(n) / gcd(phi(n), phi(sigma(n))).

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, 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, 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

Offset: 1

Author

Antti Karttunen, May 06 2022

Keywords

• nonn
• frac

Comments

Denominator of ratio A062401(n) / A000010(n), phi(sigma(n)) / phi(n).

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, A353637, A353643, A353646 (numerators).

Programs

Mathematica

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

PARI

A353644(n) = { my(ph=eulerphi(n)); (ph / gcd(eulerphi(sigma(n)), ph)); };

Formula

a(n) = A000010(n) / A353643(n) = A000010(n) / gcd(A000010(n), A062401(n)).