Voozh

A394556

a(n) is the smallest m not divisible by (n-1)! such that sigma(m) = n*m/2.

28, 91963648, 672, 4680, 32760, 17428320, 518666803200, 59485231752222033838080, 65944896818198764988659196058119700480, 668959783947499687989663212416609379593957047864830162443960320

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

OFFSET

4,1

COMMENTS

Position of a(n) among numbers with abundancy n/2 for n = 4..13: 2, 2, 2, 2, 2, 2, 3, 7, 37, 24.

An upper bound of a(14), 236008579722503605737831375688048524282888116491737299671140729618369065641395335345555374080, is given by Michel Marcus, Mar 24 2026. It has a position of at least 73 among numbers with abundancy 7 (see the link of Achim Flammenkamp).

LINKS

Table of n, a(n) for n=4..13.

Achim Flammenkamp, The Multiply Perfect Numbers Page.

G. P. Michon, Multiperfect and hemiperfect integers.

CROSSREFS

See A317681 for the smallest number with abundancy k/2 and crossrefs for numbers with abundancy k/2, for k = 4..13.

Sequence in context: A234620 A137942 A099090 * A366269 A123269 A067158

Adjacent sequences: A394552 A394553 A394555 * A394557 A394558 A394559

KEYWORD

nonn,hard

AUTHOR

Jianing Song, Mar 24 2026

STATUS

approved

URL: https://oeis.org/A394556

⇱ A394556 - OEIS