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 A045769 #57 Jun 08 2025 10:50:12 %S A045769 1,3,9,12,70,88,1888,4030,5830,32128,521728,1848964,8378368, %T A045769 34359083008,66072609790,549753192448,259708613909470, %U A045769 2251799645913088,9223372026117357568 %N A045769 Numbers k such that sigma(k) == 4 (mod k). %C A045769 Every number of the form 2^(j-1)*(2^j - 5), where 2^j - 5 is prime, is a term. See A059608. - _Jon E. Schoenfield_, Jun 02 2019 %o A045769 (PARI) isok(k) = Mod(sigma(k), k) == 4; \\ _Michel Marcus_, Jan 04 2023 %Y A045769 Contains subsequence A088832. %Y A045769 Cf. A054024, A045768, A059608, A088834, A045770, A076496. %K A045769 nonn,more %O A045769 1,2 %A A045769 _Dan Hoey_ %E A045769 a(13) from _Harvey P. Dale_, Mar 20 2011 %E A045769 Initial term 1 inserted and a(14)-a(16) from _Donovan Johnson_, Mar 01 2012 %E A045769 Term 3 inserted by _Michel Marcus_, Jan 04 2023 %E A045769 a(18) from _Jon E. Schoenfield_ confirmed, and a(17), a(19) added by _Max Alekseyev_, Jun 08 2025