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A008891 Aliquot sequence starting at 180. 3
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 (list; graph; refs; listen; history; text; internal format)
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:

PROG

(PARI) a(n, a=180)={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: A135193 A095650 A066164 * A015233 A307112 A211552

Adjacent sequences:  A008888 A008889 A008890 * A008892 A008893 A008894

KEYWORD

nonn,fini,full

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Edited by M. F. Hasler, Feb 24 2018

STATUS

approved

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Last modified November 20 02:34 EST 2019. Contains 329323 sequences. (Running on oeis4.)