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A008887
Aliquot sequence starting at 60.
3
60, 108, 172, 136, 134, 70, 74, 40, 50, 43, 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 11. - M. F. Hasler, Feb 24 2018
REFERENCES
R. K. Guy, Unsolved Problems in Number Theory, B6.
FORMULA
a(n+1) = A001065(a(n)). - R. J. Mathar, Oct 11 2017
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 *)
PROG
(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
CROSSREFS
Cf. A008885 (starting at 30), ..., A008892 (starting at 276), A098007 (length of aliquot sequences).
Sequence in context: A039398 A044001 A258700 * A217738 A351548 A182683
KEYWORD
nonn,fini,full
AUTHOR
EXTENSIONS
Edited by M. F. Hasler, Feb 24 2018
STATUS
approved