This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A366711 #9 Jan 04 2024 19:15:44
%S A366711 10,120,1560,13440,226200,2021760,32518360,274391040,4534807680,
%T A366711 51953616000,646094232960,4662793175040,97266341877120,
%U A366711 1070382142166400,13666309113600000,109897747141754880,2016918439151095000,17518491733377024000,290436363064202660760
%N A366711 a(n) = phi(12^n-1), where phi is Euler's totient function (A000010).
%H A366711 Max Alekseyev, <a href="/A366711/b366711.txt">Table of n, a(n) for n = 1..310</a>
%t A366711 EulerPhi[12^Range[30] - 1]
%o A366711 (PARI) {a(n) = eulerphi(12^n-1)}
%Y A366711 phi(k^n-1): A053287 (k=2), A295500 (k=3), A295501 (k=4), A295502 (k=5), A366623 (k=6), A366635 (k=7), A366654 (k=8), A366663 (k=9), A295503 (k=10), A366685 (k=11), this sequence (k=12).
%Y A366711 Cf. A000010, A024140, A366707, A366708, A366709, A366710, A366717, A366718.
%K A366711 nonn
%O A366711 1,1
%A A366711 _Sean A. Irvine_, Oct 17 2023