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A126016 Numbers whose aliquot sequence does not terminate in 1. 4
6, 25, 28, 95, 119, 143, 220 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Sequence continues 276?, 284, 306?, 396?, 417, 445, 496, .... Because 276,306 and 396 are all in the same family, either all 3 are present or none are. It is not known whether any aliquot sequence grows without bound; 276 is the smallest number for which this is unknown.

Additional tentative terms: 552, 562, 564, 565, 608, 650, 652, 660, 675, 685, 696, 780, 783, 790, 828, 840, 888, 909, 913, 966, 996, 1064, 1074, 1086, 1098, ... - Jean-Fran├žois Alcover, Nov 14 2013

LINKS

Table of n, a(n) for n=1..7.

Eric Weisstein's World of Mathematics, Aliquot Sequence

P. Zimmermann, Latest information

MATHEMATICA

maxAliquot = 10^45; A131884 = {}; s[1] = 1; s[n_] := DivisorSigma[1, n] - n; selQ[n_ /; n <= 5] = True; selQ[n_] := NestWhile[s, n, If[{##}[[-1]] > maxAliquot, Print["A131884: ", n]; AppendTo[A131884, n]; False, Length[{##}] < 4 || {##}[[-4 ;; -3]] != {##}[[-2 ;; -1]]] & , All] == 1; Reap[For[k = 1, k < 1100, k++, If[!selQ[k], Print[k]; Sow[k]]]][[2, 1]]

CROSSREFS

Complement of A080907. Includes A000396, A063990 and other sociable numbers, A063769, numbers whose aliquot sequence reaches a sociable number and numbers whose aliquot sequence grows without bound.

Sequence in context: A184388 A136606 A074096 * A237286 A046416 A042879

Adjacent sequences:  A126013 A126014 A126015 * A126017 A126018 A126019

KEYWORD

hard,nonn

AUTHOR

Franklin T. Adams-Watters, Dec 14 2006

STATUS

approved

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Last modified May 24 09:32 EDT 2017. Contains 286963 sequences.