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A008889
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Aliquot sequence starting at 150.
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7
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150, 222, 234, 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, 2109796, 1889486, 953914, 668966, 353578, 176792
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OFFSET
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0,1
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COMMENTS
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Start at 150, and repeatedly apply the map x -> Sum of divisors of x excluding x.
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 14. - 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 150; else sigma(f(n-1))-f(n-1); fi; end:
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MATHEMATICA
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FixedPointList[If[# > 0, DivisorSigma[1, #] - #, 0]&, 150] // Most (* Jean-François Alcover, Mar 28 2020 *)
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PROG
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(PARI) a(n, a=150)={for(i=1, n, a=sigma(a)-a); a} \\ 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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STATUS
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approved
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