A008891 - OEIS

A008891

Aliquot sequence starting at 180.

180, 366, 378, 582, 594, 846, 1026, 1374, 1386, 2358, 2790, 4698, 6192, 11540, 12736, 12664, 11096, 11104, 10820, 11944, 10466, 5236, 6860, 9940, 14252, 14308, 15218, 10894, 6746, 3376, 3196, 2852, 2524, 1900, 2440, 3140, 3496, 3704, 3256, 3584, 4600, 6560, 9316, 8072, 7078, 3542, 3370, 2714, 1606, 1058, 601, 1, 0

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OFFSET

0,1

COMMENTS

The sum-of-divisor function A000203 and aliquot parts A001065 are defined only for positive integers, so the trajectory ends when 0 is reached, here at index 52. - M. F. Hasler, Feb 24 2018

REFERENCES

R. K. Guy, Unsolved Problems in Number Theory, B6.

LINKS

T. D. Noe, Table of n, a(n) for n = 0..52

Christophe CLAVIER, Aliquot Sequences

Index entries for sequences related to aliquot parts.

FORMULA

a(n+1) = A001065(a(n)). - R. J. Mathar, Oct 11 2017

MAPLE

f := proc(n) option remember; if n = 0 then 180; else sigma(f(n-1))-f(n-1); fi; end:

MATHEMATICA

FixedPointList[If[# > 0, DivisorSigma[1, #] - #, 0]&, 180] // Most (* Jean-François Alcover, Mar 28 2020 *)