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 A019288 #28 Sep 29 2023 22:03:36 %S A019288 4404480,57669920,238608384 %N A019288 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 (2,11)-perfect numbers. %C A019288 See also the Cohen-te Riele links under A019276. %C A019288 No other terms < 5*10^11. - _Jud McCranie_, Feb 08 2012 %C A019288 a(4) > 4*10^12. - _Giovanni Resta_, Feb 26 2020 %C A019288 53283599155200, 2914255525994496 and 3887055949004800 are also terms. - _Michel Marcus_, Feb 27 2020 %H A019288 Graeme L. Cohen and Herman J. J. te Riele, <a href="http://projecteuclid.org/euclid.em/1047565640">Iterating the sum-of-divisors function</a>, Experimental Mathematics, 5 (1996), pp. 93-100. %o A019288 (PARI) isok(n) = sigma(sigma(n))/n == 11; \\ _Michel Marcus_, Feb 27 2020 %Y A019288 Cf. A019278, A019279, A019281, A019282, A019283, A019284, A019285, A019286, A019287, A019289, A019290, A019291. %K A019288 nonn,bref,more %O A019288 1,1 %A A019288 _N. J. A. Sloane_