A088011 - OEIS

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

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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