A353646 a(n) = phi(sigma(n)) / gcd(phi(n), phi(sigma(n))).

1, 2, 1, 3, 1, 2, 2, 2, 2, 3, 2, 3, 1, 4, 1, 15, 3, 4, 4, 3, 4, 6, 4, 2, 3, 1, 8, 2, 2, 3, 8, 9, 4, 9, 2, 6, 1, 8, 1, 3, 3, 8, 10, 6, 1, 12, 8, 15, 6, 3, 3, 7, 9, 16, 3, 4, 8, 6, 8, 3, 1, 16, 4, 63, 1, 12, 16, 9, 8, 2, 12, 4, 1, 1, 3, 4, 8, 2, 16, 15, 55, 9, 12, 4, 9, 20, 4, 6, 3, 3, 2, 12, 16, 24, 4, 9, 7, 18, 4, 9

Offset: 1

Author

Antti Karttunen, May 06 2022

Keywords

• nonn
• frac

Comments

Numerator 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, A353636, A353637, A353643, A353644 (denominators).

Programs

Mathematica

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

PARI

A353646(n) = { my(ps=eulerphi(sigma(n))); (ps / gcd(eulerphi(n), ps)); };

Formula

a(n) = A062401(n) / A353643(n) = A062401(n) / gcd(A062401(n), A353636(n)).