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A008889 Aliquot sequence starting at 150. 7
150, 222, 234, 312, 528, 960, 2088, 3762, 5598, 6570, 10746, 13254, 13830, 19434, 20886, 21606, 25098, 26742, 26754, 40446, 63234, 77406, 110754, 171486, 253458, 295740, 647748, 1077612, 1467588, 1956812, 2109796, 1889486, 953914, 668966, 353578, 176792 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Start at 150, and repeatedly apply the map x -> Sum of divisors of x excluding x.

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 14. - M. F. Hasler, Feb 24 2018

REFERENCES

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

LINKS

Ivan Panchenko, Table of n, a(n) for n = 0..177 (full sequence).

Christophe CLAVIER, Aliquot Sequences

Factordb, Whole sequence starting with 150

Index entries for sequences related to aliquot parts.

FORMULA

a(n) = A008888(n+1). - R. J. Mathar, Oct 28 2008

MAPLE

f := proc(n) option remember; if n = 0 then 150; else sigma(f(n-1))-f(n-1); fi; end:

MATHEMATICA

FixedPointList[If[# > 0, DivisorSigma[1, #] - #, 0]&, 150] // Most (* Jean-Fran├žois Alcover, Mar 28 2020 *)

PROG

(PARI) a(n, a=150)={for(i=1, n, a=sigma(a)-a); a} \\ M. F. Hasler, Feb 24 2018

CROSSREFS

Cf. A008885 (starting at 30), ..., A008892 (starting at 276), A098007 (length of aliquot sequences).

Sequence in context: A048706 A054729 A116185 * A184075 A207044 A292705

Adjacent sequences:  A008886 A008887 A008888 * A008890 A008891 A008892

KEYWORD

nonn,fini,full

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified October 16 19:46 EDT 2021. Contains 348044 sequences. (Running on oeis4.)