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 A373454 #46 Jan 05 2025 13:36:32 %S A373454 576,41472,2142720000,3233260800 %N A373454 Iterate the function x <- phi(sigma(x)). The sequence has the smallest member of cycles of length 4. %C A373454 130767436800000 is also a term. - _Jud McCranie_, Jun 18 2024 %C A373454 Terms are complete to 10^13. - _Jud McCranie_, Sep 14 2024 %C A373454 Terms also include 2590533833653034680320, 4911428805164059852800, 345401330417459527680000, 45369029282941832999731200, 1178793806496987670275686400000, 1241573383607207067648000000000, 3740981970485927435304960000000. - _Richard R. Forberg_, Oct 06 2024 %C A373454 Terms also include 1733855546435861719195867542454272000000. - _Richard R. Forberg_, Jan 04 2025 %e A373454 576 -> 1512 -> 1280 -> 864 -> 576, so 576 (the smallest term) is in the sequence. %o A373454 (PARI) isok(x) = my(y = eulerphi(sigma(x))); if (y > x, my(z = eulerphi(sigma(y))); if (z>x, x == eulerphi(sigma(eulerphi(sigma(z)))))); \\ _Michel Marcus_, Jun 07 2024 %Y A373454 Subsequence of A376256. %Y A373454 Cf. A000010, A000203, A001229, A095955, A095956, A373435, A373453. %K A373454 nonn,more %O A373454 1,1 %A A373454 _Jud McCranie_, Jun 06 2024