This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A008890 #22 Jul 08 2025 01:22:58
%S A008890 168,312,528,960,2088,3762,5598,6570,10746,13254,13830,19434,20886,
%T A008890 21606,25098,26742,26754,40446,63234,77406,110754,171486,253458,
%U A008890 295740,647748,1077612,1467588,1956812
%N A008890 Aliquot sequence starting at 168.
%C A008890 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 175. - _M. F. Hasler_, Feb 24 2018
%D A008890 R. K. Guy, Unsolved Problems in Number Theory, B6.
%H A008890 T. D. Noe, <a href="/A008890/b008890.txt">Table of n, a(n) for n = 0..175</a> (a(176) removed by _Georg Fischer_, Apr 28 2019)
%H A008890 Christophe Clavier, <a href="http://christophe.clavier.free.fr/Aliquot/site/Aliquot.html">Aliquot Sequences</a>
%H A008890 <a href="/index/Al#ALIQUOT">Index entries for sequences related to aliquot parts</a>.
%F A008890 a(n+1) = A001065(a(n)). - _R. J. Mathar_, Oct 11 2017
%p A008890 f := proc(n) option remember; if n = 0 then 168; else sigma(f(n-1))-f(n-1); fi; end:
%t A008890 NestList[DivisorSigma[1, #] - # &, 168, 175] (* _Alonso del Arte_, Feb 24 2018 *)
%o A008890 (PARI) a(n,a=168)={for(i=1,n,a=sigma(a)-a);a} \\ _M. F. Hasler_, Feb 24 2018
%Y A008890 Cf. A008885 (starting at 30), ..., A008892 (starting at 276), A098007 (length of aliquot sequences).
%K A008890 nonn,fini,full
%O A008890 0,1
%A A008890 _N. J. A. Sloane_
%E A008890 Edited by _M. F. Hasler_, Feb 24 2018