A074465 a(n) = gcd(n^2, sigma(n^2), phi(n^2)).

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 39, 1, 1, 21, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 1, 7, 39, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 7, 11, 1, 1, 1, 1

Offset

1,14

Comments

a(n) is odd because sigma(n^2) is odd;.

Links

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

Formula

a(n) = A074389(n^2).

Example

For n=14: gcd(196,399,84) = 7 = a(14).

Mathematica

Table[Apply[GCD, {w^2, DivisorSigma[1, w^2], EulerPhi[w^2]}], {w, 1, 128}]

Prog

(PARI) A074465(n) = gcd([n^2, sigma(n^2), eulerphi(n^2)]); \\ Antti Karttunen, Sep 07 2018

Crossrefs

Cf. A000203, A002618, A065764, A074389, A074466.

Sequence in context: A239700 A304906 A055061 * A081229 A109010 A268354

Adjacent sequences: A074462 A074463 A074464 * A074466 A074467 A074468

Keyword

nonn

Author

Labos Elemer, Aug 23 2002

Status

approved