A058073 Numbers k such that sigma(k+1) divides sigma(k), where sigma(k) is the sum of positive divisors of k.

12, 14, 70, 88, 180, 204, 206, 220, 957, 1334, 1364, 1634, 1750, 1888, 2685, 2958, 2974, 4364, 8142, 8632, 9114, 12000, 14664, 14841, 18414, 18762, 18873, 19358, 20118, 20145, 20712, 24957, 25194, 30996, 33998, 36566, 42818, 45520, 47940

Offset

1,1

Comments

The quotient (sigma(k)/sigma(k+1)) is equal to 1, 2, 3 or 4 for the first 5000 terms. - Donovan Johnson, Oct 21 2012

Links

Donovan Johnson, Table of n, a(n) for n = 1..5000

Example

12 is included because sigma(13) = 14 divides sigma(12) = 28.

Mathematica

Select[Range[50000], Mod[DivisorSigma[1, # ], DivisorSigma[1, # + 1]] == 0 &]

Crossrefs

Sequence in context: A256786 A337874 A337876 * A058951 A287916 A002926

Adjacent sequences: A058070 A058071 A058072 * A058074 A058075 A058076

Keyword

nonn

Author

Leroy Quet, Nov 11 2000

Extensions

More terms from Benoit Cloitre, Jul 27 2002

Status

approved