A069057 Numbers k such that the numerator of Sum_{d|k} 1/d > 2k.

36, 100, 144, 324, 392, 400, 576, 784, 800, 900, 968, 1296, 1352, 1575, 1600, 1936, 2304, 2450, 2500, 2704, 2916, 3136, 3600, 3872, 4356, 4624, 5184, 5408, 5776, 6050, 6272, 6400, 7744, 8100, 8450, 8464, 9216, 9248, 10000, 10404, 10816, 11552, 11664

Offset: 1

Author

Benoit Cloitre, Apr 07 2002

Keywords

• easy
• nonn

Comments

Many terms in the sequence are squares: 6^2,10^2,12^2,18^2,20^2,24^2,28^2,30^2,36^2,40^2,44^2,48^2,50^2...

Abundant numbers that are coprime to their abundance (intersection of A005101 and A014567) are all terms. Abundant numbers that are not coprime to their abundance are 4-abundant (i.e., terms of A023198, e.g., 64468800, 121726800, 168480000, ...). - Waldemar Puszkarz and Amiram Eldar, Aug 15 2024

Links

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

Crossrefs

Cf. A005101, A014567, A017665, A023198.

Programs

Mathematica

Select[Range[12000], Numerator[Total[1/Divisors@ #]] > 2 # &] (* Michael De Vlieger, May 04 2016 *)

PARI

isok(n) = numerator(sigma(n)/n) > 2*n; \\ Michel Marcus, May 04 2016