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 A028500 #38 Feb 16 2025 08:32:35 %S A028500 697,2041,1570153,62722153,10604156641,13544168521,1792155938521 %N A028500 12-hyperperfect numbers: n = 12*(sigma(n) - n - 1) + 1. %C A028500 7056410014866537089009269921 is also a term. - _Donovan Johnson_, Nov 20 2012 %C A028500 Also terms: 13^7*815787979*11621986347871 and 13^23*542800770374370512771595349. - _Giovanni Resta_, Nov 18 2019 %C A028500 a(8) >= 10^17. - _Max Alekseyev_, Nov 22 2019 %H A028500 Antal Bege, Kinga Fogarasi, <a href="http://www.acta.sapientia.ro/acta-math/C1-1/MATH1-6.PDF">Generalized perfect numbers</a>, Acta Univ. Sapientiae, Math., 1 (2009), 73-82. %H A028500 Judson S. McCranie, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL3/mccranie.html">A Study of Hyperperfect Numbers</a>, Journal of Integer Sequences, Vol. 3 (2000), Article 00.1.3. %H A028500 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HyperperfectNumber.html">Hyperperfect Number</a> %o A028500 (PARI) isok(n) = 12*(sigma(n) - n - 1) + 1 == n; \\ _Michel Marcus_, Nov 18 2019 %Y A028500 Cf. A000396, A007593, A028499, A028501, A028502, A034916, A220290. %K A028500 hard,more,nonn %O A028500 1,1 %A A028500 _Jud McCranie_ %E A028500 a(7) from _Donovan Johnson_, Nov 20 2012