A008890 Aliquot sequence starting at 168.

168, 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

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• fini
• full

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 175. - 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..175 (a(176) removed by _Georg Fischer_, Apr 28 2019)
• Christophe Clavier, Aliquot Sequences
• Index entries for sequences related to aliquot parts.

Crossrefs

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

Programs

Maple

f := proc(n) option remember; if n = 0 then 168; else sigma(f(n-1))-f(n-1); fi; end:

Mathematica

NestList[DivisorSigma[1, #] - # &, 168, 175] (* Alonso del Arte, Feb 24 2018 *)

PARI

a(n,a=168)={for(i=1,n,a=sigma(a)-a);a} \\ M. F. Hasler, Feb 24 2018

Formula

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

Extensions

Edited by M. F. Hasler, Feb 24 2018