A265713 Numbers k such that floor(Sum_{d|k} 1 / sigma(d)) = 3.

110880, 166320, 221760, 277200, 327600, 332640, 360360, 388080, 393120, 415800, 443520, 471240, 480480, 491400, 498960, 526680, 540540, 554400, 556920, 582120, 589680, 600600, 622440, 637560, 655200, 665280, 693000, 720720, 776160, 786240, 803880, 831600

Offset: 1

Author

Jaroslav Krizek, Dec 25 2015

Keywords

• nonn

Comments

Numbers k such that A265710(k) = floor(A265708(k) / A069934(k)) = floor(A265709(k) / A265710(k)) = 3.

See A265714(n) = the smallest number k such that floor(Sum_{d|k} 1/sigma(d)) = n.

Examples

			110880 is a term because floor(Sum_{d|110880} 1/sigma(d)) = floor(22333/7440) = 3.
		

Links

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

Crossrefs

Cf. A069934, A000203, A265708, A265709, A265710, A265711, A265712, A265714, A266227, A266228.

Programs

Magma

[n: n in [1..1000000] | Floor(&+[1/SumOfDivisors(d): d in Divisors(n)]) eq 3]

Mathematica

Select[Range[10^5, 9*10^5], Floor[Sum[1/DivisorSigma[1, d], {d, Divisors@ #}]] == 3 &] (* Michael De Vlieger, Dec 31 2015 *)

PARI

isok(n) = floor(sumdiv(n, d, 1/sigma(d))) == 3; \\ Michel Marcus, Dec 27 2015