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 A019281 #23 Sep 29 2023 22:03:02 %S A019281 8,21,512 %N A019281 Let sigma_m (n) be result of applying sum-of-divisors function m times to n; call n (m,k)-perfect if sigma_m (n) = k*n; sequence gives the (2,3)-perfect numbers. %C A019281 See also the Cohen-te Riele links under A019276. %C A019281 No further term < 10^9 [see Table 1]. %C A019281 No other terms < 5*10^11. - _Jud McCranie_, Feb 08 2012 %C A019281 a(4) > 4*10^12, if it exists. - _Giovanni Resta_, Feb 26 2020 %H A019281 Graeme L. Cohen and Herman J. J. te Riele, <a href="http://www.emis.de/journals/EM/expmath/volumes/5/5.html">Iterating the sum-of-divisors function</a>, Experimental Mathematics, 5 (1996), pp. 93-100. %H A019281 Experimental Mathematics, <a href="http://www.emis.de/journals/EM/">Home Page</a>. %Y A019281 Cf. A019278, A019279, A019282, A019283, A019284, A019285, A019286, A019287, A019288, A019289, A019290, A019291. %K A019281 nonn,bref,more %O A019281 1,1 %A A019281 _N. J. A. Sloane_