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%I #14 Jan 04 2024 19:04:29
%S 4,24,168,864,6200,30240,223944,1119744,7457184,37200000,277618528,
%T 1254113280,10445497920,51618196224,365601600000,1770091315200,
%U 13439285266176,62336092492800,484935499902880,2179146240000000,17141125020596640,86330728271779200
%N a(n) = phi(6^n-1), where phi is Euler's totient function (A000010).
%H Max Alekseyev, <a href="/A366623/b366623.txt">Table of n, a(n) for n = 1..420</a>
%F a(n) = A000010(A024062(n)). - _Paul F. Marrero Romero_, Oct 23 2023
%t EulerPhi[6^Range[22] - 1] (* _Paul F. Marrero Romero_, Oct 23 2023 *)
%o (PARI) {a(n) = eulerphi(6^n-1)}
%Y phi(k^n-1): A053287 (k=2), A295500 (k=3), A295501 (k=4), A295502 (k=5), this sequence (k=6), A366635 (k=7), A366654 (k=8), A366663 (k=9), A295503 (k=10), A366685 (k=11), A366711 (k=12).
%Y Cf. A024062, A000010, A295502, A366620, A366621, A366622.
%K nonn
%O 1,1
%A _Sean A. Irvine_, Oct 14 2023