A348697 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A348697

Numbers m such that there is at least two smaller numbers k < m with the same harmonic mean of divisors as m.

321048, 448335, 1284192, 1605240, 1672125, 1862190, 3531528, 5016375, 5457816, 6420960, 7384104, 7621695, 8026200, 9310392, 9952488, 10311705, 11878776, 13001715, 13035330, 13162968, 13805064, 13898385, 14126112, 15089256, 16588395, 17015544, 17657640, 17836000

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

What is the least term m with more than two smaller numbers k with the same harmonic mean of divisors as m?

LINKS

Table of n, a(n) for n=1..28.

EXAMPLE

321048 is a term since the harmonic mean of divisors of 321048 is 3528/125, and it is also the harmonic mean of divisors of both 201096 and 296352 which are smaller than 321048.

MATHEMATICA

h = Table[DivisorSigma[0, n]/DivisorSigma[-1, n], {n, 1, 2*10^6}]; i = Position[(t = Tally[h])[[;; , 2]], _?(# > 2 &)] // Flatten; Position[h, #][[3 ;; -1]] & /@ t[[i, 1]] // Flatten // Sort

CROSSREFS

Cf. A099377, A099378, A348696.

Sequence in context: A205931 A236318 A348827 * A097937 A244565 A362874

Adjacent sequences: A348694 A348695 A348696 * A348698 A348699 A348700

KEYWORD

nonn

AUTHOR

Amiram Eldar, Oct 30 2021

STATUS

approved