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 A067680 #19 Apr 09 2020 01:55:50 %S A067680 6,21,54,75,441,1071,4191,9315,58311,4197375,7685151,36997695, %T A067680 268460031,1073790975,17180065791,13517087570210304,18014398710808575, %U A067680 288230376957018111 %N A067680 Numbers k such that sigma(2k + 2) = 4k. %C A067680 If k is a term, then 2*k + 2 is a term of A125246. - _Jinyuan Wang_, Apr 08 2020 %o A067680 (PARI) isok(k) = sigma(2*k+2) == 4*k; \\ _Michel Marcus_, Apr 06 2020 %Y A067680 Cf. A000203, A125246. %K A067680 nonn,more %O A067680 1,1 %A A067680 _Benoit Cloitre_, Feb 04 2002 %E A067680 a(9) from _Benoit Cloitre_ and Neven Juric (neven.juric(AT)apis-it.hr), May 21 2004 %E A067680 a(10)-a(15) from _Donovan Johnson_, Jan 31 2009 %E A067680 a(16)-a(18) from _Jinyuan Wang_, Apr 06 2020