A091260 Denominator of sigma_3(n)/sigma_2(n).

1, 5, 5, 21, 13, 25, 25, 17, 91, 65, 61, 15, 85, 125, 65, 11, 145, 455, 181, 13, 125, 305, 265, 85, 651, 425, 41, 525, 421, 325, 481, 455, 305, 725, 325, 1911, 685, 181, 425, 17, 841, 625, 925, 427, 169, 1325, 1105, 55, 817, 1085, 725, 255, 1405, 205, 793, 425, 181

Offset: 1

Author

Labos Elemer, Feb 12 2004

Keywords

• easy
• nonn
• frac

Comments

If n is an odd prime then a(n) = A001844((n-1)/2). - Robert Israel, Jan 26 2018

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A001158, A001157, A000203, A091258, A091259, A298754 (numerator), A001844.

Programs

Maple

seq(denom(numtheory:-sigma[3](n)/numtheory:-sigma[2](n)),n=1..100); # Robert Israel, Jan 26 2018

Mathematica

Denominator[Table[DivisorSigma[3,n]/DivisorSigma[2,n],{n,60}]] (* Harvey P. Dale, Nov 03 2011 *)

PARI

a(n) = my(f = factor(n)); denominator(sigma(f, 3)/sigma(f, 2)); \\ Amiram Eldar, Dec 20 2024