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 A067192 #22 Feb 17 2021 04:17:12 %S A067192 10,20,52,232,976,1332,65152,261376,4191232,67096576,274877120512, %T A067192 4398043365376 %N A067192 Composite c such that sigma(c)==2 (mod phi(c)). %C A067192 a(12) > 10^12. 4398043365376, 70368731594752 and 72057593635274752 are also terms. - _Donovan Johnson_, Feb 29 2012 %C A067192 a(13) > 10^13. If 2^k-3 is prime (A050414), then 2^(k-2)*(2^k-3) is a term. Up to 10^13 the only term not of this form is 1332. - _Giovanni Resta_, Mar 29 2020 %o A067192 (PARI) isok(c) = !isprime(c) && ((sigma(c) % eulerphi(c)) == 2); \\ _Michel Marcus_, Feb 17 2021 %Y A067192 Cf. A050414, A067193. %K A067192 nonn,more %O A067192 1,1 %A A067192 _Benoit Cloitre_, Feb 19 2002 %E A067192 a(8)-a(10) from _Donovan Johnson_, Dec 14 2009 %E A067192 a(11) from _Donovan Johnson_, Feb 29 2012 %E A067192 a(12) from _Giovanni Resta_, Mar 29 2020