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 A295503 #17 Feb 16 2025 08:33:52
%S A295503 6,60,648,6000,64800,466560,6637344,58752000,648646704,5890320000,
%T A295503 66663457344,461894400000,6458084523072,60339430569600,
%U A295503 610154104320000,5529599115264000,66666634474902192,441994921381739520,6666666666666666660,58301444908800000000
%N A295503 a(n) = phi(10^n-1), where phi is Euler's totient function (A000010).
%H A295503 Max Alekseyev, <a href="/A295503/b295503.txt">Table of n, a(n) for n = 1..352</a>
%H A295503 Eric W. Weisstein, <a href="https://mathworld.wolfram.com/TotientFunction.html">MathWorld: Totient Function</a>
%H A295503 Wikipedia, <a href="http://en.wikipedia.org/wiki/Euler%27s_phi_function">Euler's totient function</a>
%F A295503 a(n) = n*A295497(n).
%F A295503 a(n) = A000010(A002283(n)). - _Michel Marcus_, Nov 25 2017
%t A295503 Array[ EulerPhi[10^# - 1] &, 20] (* _Robert G. Wilson v_, Nov 22 2017 *)
%o A295503 (PARI) {a(n) = eulerphi(10^n-1)}
%Y A295503 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), this sequence (k=10), A366685 (k=11), A366711 (k=12).
%Y A295503 Cf. A000010, A002283.
%K A295503 nonn
%O A295503 1,1
%A A295503 _Seiichi Manyama_, Nov 22 2017