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 A373453 #56 Jan 05 2025 13:36:19 %S A373453 16,1200,15552,67392,272160,69672960000 %N A373453 Iterate the function x <- phi(sigma(x)). The sequence has the smallest member of cycles of length 3. %C A373453 69672960000 is also a term in the sequence. %C A373453 a(7) <= 2704853606400. The numbers 242595672883200000, 66217181184000000000 and 185577469193591193600 are also terms. - _Giorgos Kalogeropoulos_, Jun 18 2024 %C A373453 4672651788288000 is also a term. - _Jud McCranie_, Jun 18 2024 %C A373453 The sequence is complete through 10^13. - _Jud McCranie_, Sep 14 2024 %H A373453 Richard R. Forberg, <a href="/A373453/a373453.txt">Additional terms</a>, Nov 2024. %e A373453 16 -> 30 -> 24 -> 16, so 16 (the smallest term) is in the sequence. %o A373453 (PARI) isok(x) = my(y = eulerphi(sigma(x))); if (y > x, my(z = eulerphi(sigma(y))); if (z > x, x == eulerphi(sigma(z)))); \\ _Michel Marcus_, Jun 07 2024 %Y A373453 Subsequence of A376256. %Y A373453 Cf. A001229, A095955, A095956, A373435, A373454. %K A373453 nonn,more %O A373453 1,1 %A A373453 _Jud McCranie_, Jun 06 2024 %E A373453 a(6) from _Giorgos Kalogeropoulos_, Jun 18 2024