A091258 Denominator of sigma_3(n)/sigma(n).

1, 1, 1, 7, 1, 1, 1, 1, 13, 1, 1, 1, 1, 1, 1, 1, 1, 13, 1, 1, 1, 1, 1, 1, 31, 1, 1, 7, 1, 1, 1, 7, 1, 1, 1, 91, 1, 1, 1, 1, 1, 1, 1, 7, 13, 1, 1, 1, 19, 31, 1, 7, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 13, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 31, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 13, 1, 7, 1, 1, 1, 1, 1, 19, 13

Offset: 1

Author

Labos Elemer, Feb 12 2004

Keywords

• easy
• nonn
• frac

Comments

Conjecture: The set of distinct terms is A004611. - Michel Marcus, Aug 10 2024

Links

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

Crossrefs

Cf. A001158, A000203, A091259 (numerators), A091260.

Cf. A002476, A004611.

Programs

Mathematica

Denominator[Table[DivisorSigma[3,n]/DivisorSigma[1,n],{n,100}]] (* Harvey P. Dale, Oct 06 2017 *)

PARI

a(n) = denominator(sigma(n, 3)/sigma(n)); \\ Michel Marcus, Dec 29 2013