A366658 - OEIS

%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