A074389 a(n) = gcd(n, sigma(n), phi(n)).

1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 4, 1, 2, 1, 1, 1, 3, 1, 2, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 6, 1, 4, 3, 2, 1, 4, 1, 1, 1, 2, 1, 6, 1, 8, 1, 2, 1, 4, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 1, 4, 1, 6, 1, 2, 1, 2, 1, 4, 1, 2, 1, 4, 1, 6, 1, 4, 1, 2, 1, 4, 1, 1, 3, 1, 1, 2, 1, 2, 3

Offset: 1

Author

Labos Elemer, Aug 23 2002

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..65537

Crossrefs

Cf. A000010, A000203, A073815, A050399, A009194, A009195, A009223, A074465, A074466.

In the old definition the erroneously given formula gcd(n, A000005(n), A000010(n)) is now sequence A318459. - Antti Karttunen, Sep 07 2018

Programs

Mathematica

Table[Apply[GCD, {w, DivisorSigma[1, w], EulerPhi[w]}], {w, 1, 128}]

PARI

A074389(n) = gcd([n, sigma(n), eulerphi(n)]); \\ Antti Karttunen, Sep 07 2018

Formula

a(n) = gcd(n, A000010(n), A000203(n)).

a(n) = gcd(n, A009223(n)). - Antti Karttunen, Sep 07 2018

Extensions

Name corrected by Antti Karttunen, Sep 07 2018