A008886 - OEIS

A008886

Aliquot sequence starting at 42.

42, 54, 66, 78, 90, 144, 259, 45, 33, 15, 9, 4, 3, 1, 0

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

REFERENCES

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

LINKS

Table of n, a(n) for n=0..14.

Christophe CLAVIER, Aliquot Sequences

Index entries for sequences related to aliquot parts.

FORMULA

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

a(n) = A008885(n+1). - R. J. Mathar, Jan 12 2024

MAPLE

f := proc(n) option remember; if n = 0 then 42; else sigma(f(n-1))-f(n-1); fi; end:

MATHEMATICA

Join[NestList[DivisorSigma[1, #]-#&, 42, 14], PadRight[{}, 60, 0]] (* Harvey P. Dale, Apr 28 2014 *)

PROG

(PARI) a(n, a=42)={for(i=1, n, a=sigma(a)-a); a} \\ M. F. Hasler, Feb 24 2018

CROSSREFS

Cf. A098007 (length of aliquot sequences); some other examples: A008885 (starting at 30) .. A008892 (starting at 276), A014360 (starting at 552) .. A014365 (starting at 1134), see link to index for a more complete list.

Sequence in context: A156394 A083244 A125009 * A341129 A182147 A029695

Adjacent sequences: A008883 A008884 A008885 * A008887 A008888 A008889

KEYWORD

nonn,fini,full

AUTHOR

N. J. A. Sloane

EXTENSIONS

Edited by M. F. Hasler, Feb 24 2018

STATUS

approved