A335053 - OEIS

A335053

Odd bi-unitary abundant numbers whose bi-unitary abundancy is closer to 2 than that of any smaller odd bi-unitary abundant number.

945, 25515, 46035, 49875, 83265, 354585, 359205, 361515, 366135, 382305, 389235, 396165, 400785, 403095, 407715, 414645, 416955, 423885, 430815, 437745, 442365, 13351635, 132335385, 159030135, 1756753845, 6561644355, 10394173335, 13455037365, 37456183215

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OFFSET

1,1

COMMENTS

The bi-unitary abundancy of a number k is bsigma(k)/k, where bsigma(k) is the sum of bi-unitary divisors of k (A188999).

LINKS

Table of n, a(n) for n=1..29.

EXAMPLE

The bi-unitary abundancies of the first terms are 2.031..., 2.005..., 2.0019..., 2.0018..., 2.0015..., ...

MATHEMATICA

fun[p_, e_] := If[OddQ[e], (p^(e + 1) - 1)/(p - 1), (p^(e + 1) - 1)/(p - 1) - p^(e/2)]; bsigma[1] = 1; bsigma[n_] := Times @@ (fun @@@ FactorInteger[n]); seq = {}; r = 3; Do[s = bsigma[n]/n; If[s > 2 && s < r, AppendTo[seq, n]; r = s], {n, 1, 10^6, 2}]; seq

CROSSREFS

Cf. A188999, A188263, A293186, A302571, A335052, A335055.

Sequence in context: A294027 A127666 A274756 * A290034 A335055 A133818

Adjacent sequences: A335050 A335051 A335052 * A335054 A335055 A335056

KEYWORD

nonn

AUTHOR

Amiram Eldar, May 21 2020

STATUS

approved