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 A295497 #27 Jun 17 2024 15:46:41
%S A295497 6,30,216,1500,12960,77760,948192,7344000,72071856,589032000,
%T A295497 6060314304,38491200000,496775732544,4309959326400,40676940288000,
%U A295497 345599944704000,3921566733817776,24555273410096640,350877192982456140,2915072245440000000
%N A295497 a(n) = phi(10^n-1)/n, where phi is Euler's totient function (A000010).
%H A295497 Seiichi Manyama, <a href="/A295497/b295497.txt">Table of n, a(n) for n = 1..50</a>
%H A295497 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TotientFunction.html">Totient Function</a>.
%H A295497 Wikipedia, <a href="https://en.wikipedia.org/wiki/Euler%27s_totient_function">Euler's totient function</a>.
%t A295497 Array[EulerPhi[10^# - 1]/# &, 25] (* _Paolo Xausa_, Jun 17 2024 *)
%o A295497 (PARI) {a(n) = eulerphi(10^n-1)/n}
%Y A295497 Column k=10 of A369291.
%Y A295497 phi(k^n-1)/n: A011260 (k=2), A027385 (k=3), A027695 (k=4), A027741 (k=5), A295496 (k=6), A027743 (k=7), A027744 (k=8), A027745 (k=9), this sequence (k=10), A319166 (k=11).
%K A295497 nonn
%O A295497 1,1
%A A295497 _Seiichi Manyama_, Nov 22 2017