A366759 a(n) = phi(n!-1), where phi is Euler's totient function (A000010).
1, 4, 22, 96, 718, 5038, 38544, 329780, 3503640, 33166848, 479001598, 6223425864, 87178291198, 1168577230080, 20915909651520, 332351050332096, 6293831116536216, 121458761380686016, 2432882508925834560, 48311155748401677120, 1113688776127971818016
Offset: 2
Keywords
Programs
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Mathematica
EulerPhi[Range[2,25]!-1] (* Paolo Xausa, Oct 21 2023 *)
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PARI
{a(n) = eulerphi(n!-1)} -
Python
from math import factorial from sympy import totient def A366759(n): return totient(factorial(n)-1) # Chai Wah Wu, Oct 20 2023