A088011 Even and odd solutions to abs(sigma(x)-2x) <= log(x). Numbers n whose abundance-radius does not exceed log(n).

4, 6, 8, 10, 16, 20, 28, 32, 64, 70, 88, 104, 110, 128, 136, 152, 256, 464, 496, 512, 592, 650, 884, 1024, 1155, 1888, 1952, 2048, 2144, 4030, 4096, 5830, 8128, 8192, 8384, 8925, 11096, 16384, 17816, 18632, 18904, 32128, 32445, 32768, 32896, 33664, 45356

Offset

1,1

Comments

See A088012 for the subsequence of odd terms, only 7 being known up to 10^13. - M. F. Hasler, Feb 21 2017

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Mathematica

abu[x_] := Abs[DivisorSigma[1, x]-2*x] Do[If[ !Greater[abu[n], Log[n]//N], Print[n]], {n, 1, 100000}]

Prog

(PARI) (is(n)=abs(sigma(n)-2*n)<log(n)); select(is, [1..5000]) \\ M. F. Hasler, Feb 21 2017

Crossrefs

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

Sequence in context: A280739 A353917 A117347 * A289424 A050835 A369139

Adjacent sequences: A088008 A088009 A088010 * A088012 A088013 A088014

Keyword

nonn

Author

Labos Elemer, Oct 20 2003

Status

approved