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%I #21 Jan 09 2024 18:46:20
%S 1,6,48,324,3840,19800,186624,1365336,16515072,84768120,760320000,
%T 5632621632,64258375680,366369658200,3105655160832,20140520400000,
%U 280012271910912,1495522910085120,12824556668190720,95907982079387520,1080582572777472000,5688765822212629632
%N a(n) = phi(8^n+1), where phi is Euler's totient function (A000010).
%H Max Alekseyev, <a href="/A366658/b366658.txt">Table of n, a(n) for n = 0..502</a>
%F a(n) = A000010(A062395(n)). - _Paul F. Marrero Romero_, Nov 06 2023
%F a(n) = A053285(3*n). - _Max Alekseyev_, Jan 09 2024
%t EulerPhi[8^Range[0, 21] + 1] (* _Paul F. Marrero Romero_, Oct 17 2023 *)
%o (PARI) {a(n) = eulerphi(8^n+1)}
%o (Python)
%o from sympy import totient
%o def A366658(n): return totient((1<<3*n)+1) # _Chai Wah Wu_, Oct 15 2023
%Y Cf. A062395, A000010, A057936, A274905, A366654, A366655, A366656, A366657, A366671.
%Y Cf. A053285, A366579, A366608, A366618, A366630, A366639, A366667, A366669, A366690, A366716.
%K nonn
%O 0,2
%A _Sean A. Irvine_, Oct 15 2023
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