%I #18 Oct 26 2023 20:14:59
%S 2,12,128,1400,30240,264992,6635520,141087744,5890320000,114117380608,
%T 4662793175040,99053063903040,5470524984113280,167080949856000000,
%U 9208981628670443520,413582117375670921216,29531731481729468006400,659473218553437863041320
%N a(n) is phi(n^n-1) where phi is the Euler totient function.
%H Robert G. Wilson v, <a href="/A366821/b366821.txt">Table of n, a(n) for n = 2..102</a>
%F a(n) = A000010(A048861(n)).
%p a:= n-> numtheory[phi](n^n-1):
%p seq(a(n), n=2..20); # _Alois P. Heinz_, Oct 26 2023
%t Array[EulerPhi[#^# - 1] &, 18, 2] (* _Michael De Vlieger_, Oct 24 2023 *)
%o (PARI) a(n) = eulerphi(n^n-1);
%Y Cf. A000010, A048861, A064447, A366822.
%K nonn
%O 2,1
%A _Sean A. Irvine_, Oct 24 2023
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