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 A045477 #15 Mar 28 2020 10:13:57 %S A045477 840,2040,4440,9240,25320,51000,117480,271320,765480,1531320,3721800, %T A045477 7817640,15635640,32899560,65799480,139098120,349027320,699333000, %U A045477 1597611000,3386944680,9543610200,20041583280 %N A045477 Aliquot sequence starting at 840 (reaches 1 at 747th term). %D A045477 A. W. P. Guy and R. K. Guy, A record aliquot sequence, pp. 557-559 of Mathematics of Computation 1943-1993 (Vancouver, 1993), Proc. Symp. Appl. Math., Vol. 48, Amer. Math. Soc. 1994. %H A045477 T. D. Noe, <a href="/A045477/b045477.txt">Table of n, a(n) for n = 0..748</a> %H A045477 Christophe CLAVIER, <a href="http://christophe.clavier.free.fr/Aliquot/site/Aliquot.html">Aliquot Sequences</a> %F A045477 a(n+1) = A001065(a(n)). - _R. J. Mathar_, Oct 11 2017 %t A045477 FixedPointList[If[# > 0, DivisorSigma[1, #] - #, 0]&, 840] // Most (* _Jean-François Alcover_, Mar 28 2020 *) %K A045477 nonn,fini,full %O A045477 0,1 %A A045477 _N. J. A. Sloane_