A366759 - OEIS

%I #13 Oct 21 2023 16:00:49

%S 1,4,22,96,718,5038,38544,329780,3503640,33166848,479001598,

%T 6223425864,87178291198,1168577230080,20915909651520,332351050332096,

%U 6293831116536216,121458761380686016,2432882508925834560,48311155748401677120,1113688776127971818016

%N a(n) = phi(n!-1), where phi is Euler's totient function (A000010).

%F a(n) = A000010(A033312(n)).

%t EulerPhi[Range[2,25]!-1] (* _Paolo Xausa_, Oct 21 2023 *)

%o (PARI) {a(n) = eulerphi(n!-1)}

%o (Python)

%o from math import factorial

%o from sympy import totient

%o def A366759(n): return totient(factorial(n)-1) # _Chai Wah Wu_, Oct 20 2023

%Y Cf. A033312, A000010, A048855, A366760.

%K nonn

%O 2,2

%A _Sean A. Irvine_, Oct 20 2023