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

Author

Leroy Quet, Nov 11 2000

Keywords

• nonn

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

Examples

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

Links

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

Programs

Mathematica

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

Extensions

More terms from Benoit Cloitre, Jul 27 2002