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A008889 Aliquot sequence starting at 150.

%I A008889 #46 Mar 28 2020 07:59:23
%S A008889 150,222,234,312,528,960,2088,3762,5598,6570,10746,13254,13830,19434,
%T A008889 20886,21606,25098,26742,26754,40446,63234,77406,110754,171486,253458,
%U A008889 295740,647748,1077612,1467588,1956812,2109796,1889486,953914,668966,353578,176792
%N A008889 Aliquot sequence starting at 150.
%C A008889 Start at 150, and repeatedly apply the map x -> Sum of divisors of x excluding x.
%C A008889 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
%D A008889 R. K. Guy, Unsolved Problems in Number Theory, B6.
%H A008889 Ivan Panchenko, <a href="/A008889/b008889.txt">Table of n, a(n) for n = 0..177</a> (full sequence).
%H A008889 Christophe CLAVIER, <a href="http://christophe.clavier.free.fr/Aliquot/site/Aliquot.html">Aliquot Sequences</a>
%H A008889 Factordb, <a href="http://www.factordb.com/sequences.php?se=1&amp;aq=150&amp;action=all&amp;fr=0&amp;to=100">Whole sequence starting with 150</a>
%H A008889 <a href="/index/Al#ALIQUOT">Index entries for sequences related to aliquot parts</a>.
%F A008889 a(n) = A008888(n+1). - _R. J. Mathar_, Oct 28 2008
%p A008889 f := proc(n) option remember; if n = 0 then 150; else sigma(f(n-1))-f(n-1); fi; end:
%t A008889 FixedPointList[If[# > 0, DivisorSigma[1, #] - #, 0]&, 150] // Most (* _Jean-François Alcover_, Mar 28 2020 *)
%o A008889 (PARI) a(n,a=150)={for(i=1,n,a=sigma(a)-a);a} \\ _M. F. Hasler_, Feb 24 2018
%Y A008889 Cf. A008885 (starting at 30), ..., A008892 (starting at 276), A098007 (length of aliquot sequences).
%K A008889 nonn,fini,full
%O A008889 0,1
%A A008889 _N. J. A. Sloane_