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 A074906 #14 Mar 28 2020 10:14:04 %S A074906 1521,858,1158,1170,2106,2976,5088,8520,17400,38400,88452,196924, %T A074906 228004,255836,255892,339948,708372,1392748,1392804,2631580,3684548, %U A074906 3684604,4502876,4502932,4630444,5343604,5343660,13185396,26489484 %N A074906 Aliquot sequence starting at 1521. %C A074906 This aliquot sequence starts with the least odd number such that the sequence does not repeat a term after 20 or fewer terms. %D A074906 R. K. Guy, Unsolved Problems in Number Theory, B6. %H A074906 T. D. Noe, <a href="/A074906/b074906.txt">Table of n, a(n) for n = 0..169</a> %H A074906 Christophe CLAVIER, <a href="http://christophe.clavier.free.fr/Aliquot/site/Aliquot.html">Aliquot Sequences</a> %F A074906 a(n+1) = A001065(a(n)). - _R. J. Mathar_, Oct 11 2017 %e A074906 a(0)= 1521, a(1) = sigma(1521) - 1521 = 858. %t A074906 FixedPointList[If[# > 0, DivisorSigma[1, #] - #, 0]&, 1521] // Most (* _Jean-François Alcover_, Mar 28 2020 *) %Y A074906 Cf. A008888, A008889. %K A074906 nonn,fini,full %O A074906 0,1 %A A074906 Robert A. Stump (bee_ess107(AT)msn.com), Sep 30 2002