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 A366759 #13 Oct 21 2023 16:00:49
%S A366759 1,4,22,96,718,5038,38544,329780,3503640,33166848,479001598,
%T A366759 6223425864,87178291198,1168577230080,20915909651520,332351050332096,
%U A366759 6293831116536216,121458761380686016,2432882508925834560,48311155748401677120,1113688776127971818016
%N A366759 a(n) = phi(n!-1), where phi is Euler's totient function (A000010).
%F A366759 a(n) = A000010(A033312(n)).
%t A366759 EulerPhi[Range[2,25]!-1] (* _Paolo Xausa_, Oct 21 2023 *)
%o A366759 (PARI) {a(n) = eulerphi(n!-1)}
%o A366759 (Python)
%o A366759 from math import factorial
%o A366759 from sympy import totient
%o A366759 def A366759(n): return totient(factorial(n)-1) # _Chai Wah Wu_, Oct 20 2023
%Y A366759 Cf. A033312, A000010, A048855, A366760.
%K A366759 nonn
%O A366759 2,2
%A A366759 _Sean A. Irvine_, Oct 20 2023