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A008887
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Aliquot sequence starting at 60.
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3
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60, 108, 172, 136, 134, 70, 74, 40, 50, 43, 1, 0
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history;
text;
internal format)
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OFFSET
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0,1
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COMMENTS
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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
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REFERENCES
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R. K. Guy, Unsolved Problems in Number Theory, B6.
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LINKS
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FORMULA
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MAPLE
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f := proc(n) option remember; if n = 0 then 60; else sigma(f(n-1))-f(n-1); fi; end:
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MATHEMATICA
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NestList[If[#==0, 0, DivisorSigma[1, #]-#]&, 60, 80] (* Harvey P. Dale, Nov 29 2013 *)
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn,fini,full
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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