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