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 A008886 #23 Jul 08 2025 01:22:41
%S A008886 42,54,66,78,90,144,259,45,33,15,9,4,3,1,0
%N A008886 Aliquot sequence starting at 42.
%C A008886 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 A008886 R. K. Guy, Unsolved Problems in Number Theory, B6.
%H A008886 Christophe CLAVIER, <a href="http://christophe.clavier.free.fr/Aliquot/site/Aliquot.html">Aliquot Sequences</a>
%H A008886 <a href="/index/Al#ALIQUOT">Index entries for sequences related to aliquot parts</a>.
%F A008886 a(n+1) = A001065(a(n)). - _R. J. Mathar_, Oct 11 2017
%F A008886 a(n) = A008885(n+1). - _R. J. Mathar_, Jan 12 2024
%p A008886 f := proc(n) option remember; if n = 0 then 42; else sigma(f(n-1))-f(n-1); fi; end:
%t A008886 Join[NestList[DivisorSigma[1,#]-#&,42,14],PadRight[{},60,0]] (* _Harvey P. Dale_, Apr 28 2014 *)
%o A008886 (PARI) a(n,a=42)={for(i=1,n,a=sigma(a)-a);a} \\ _M. F. Hasler_, Feb 24 2018
%Y A008886 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.
%K A008886 nonn,fini,full
%O A008886 0,1
%A A008886 _N. J. A. Sloane_
%E A008886 Edited by _M. F. Hasler_, Feb 24 2018