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

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 *)

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