A088010 Odd numbers n such that abs(sigma(n)-2n) <= n^(1/3). Abundance-radius = abs(sigma(n)-2n) does not exceed cubic root of n and n is odd.

1, 315, 1155, 8415, 8925, 31815, 32445, 33705, 34335, 78975, 351351, 430815, 437745, 442365, 449295, 730125, 1805475, 7667625, 13800465, 14571585, 16029405, 16286445, 20297745, 20355825, 20487159, 21003885, 22982505, 23082885

Offset: 1

Author

Labos Elemer, Oct 20 2003

Keywords

• nonn

Links

• Donovan Johnson, Table of n, a(n) for n = 1..100

Crossrefs

Cf. A077374, A088007-A088012, A000396, A000079, A005100, A005101.

Programs

Mathematica

abu[x_] := Abs[DivisorSigma[1, x]-2*x] Do[If[ !Greater[abu[n], n^(1/3)//N]&&OddQ[n], Print[n]], {n, 1, 100000}]

PARI

isok(n) = (n % 2) && (abs(sigma(n)-2*n) < sqrtn(n, 3)); \\ Michel Marcus, Nov 10 2017

Extensions

a(17)-a(28) from Donovan Johnson, Feb 01 2009