%I #27 Jun 17 2024 15:46:41

%S 6,30,216,1500,12960,77760,948192,7344000,72071856,589032000,

%T 6060314304,38491200000,496775732544,4309959326400,40676940288000,

%U 345599944704000,3921566733817776,24555273410096640,350877192982456140,2915072245440000000

%N a(n) = phi(10^n-1)/n, where phi is Euler's totient function (A000010).

%H Seiichi Manyama, <a href="/A295497/b295497.txt">Table of n, a(n) for n = 1..50</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TotientFunction.html">Totient Function</a>.

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Euler%27s_totient_function">Euler's totient function</a>.

%t Array[EulerPhi[10^# - 1]/# &, 25] (* _Paolo Xausa_, Jun 17 2024 *)

%o (PARI) {a(n) = eulerphi(10^n-1)/n}

%Y Column k=10 of A369291.

%Y 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 nonn

%O 1,1

%A _Seiichi Manyama_, Nov 22 2017