A008887 Aliquot sequence starting at 60.

60, 108, 172, 136, 134, 70, 74, 40, 50, 43, 1, 0

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

References

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

Links

• 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 60; else sigma(f(n-1))-f(n-1); fi; end:

Mathematica

NestList[If[#==0,0,DivisorSigma[1,#]-#]&,60,80] (* Harvey P. Dale, Nov 29 2013 *)

PARI

a(n,a=60)=for(i=1,n,a=sigma(a)-a);a \\ Will raise an error for n > 11, in agreement with the definition. - 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