A295497 a(n) = phi(10^n-1)/n, where phi is Euler's totient function (A000010).

6, 30, 216, 1500, 12960, 77760, 948192, 7344000, 72071856, 589032000, 6060314304, 38491200000, 496775732544, 4309959326400, 40676940288000, 345599944704000, 3921566733817776, 24555273410096640, 350877192982456140, 2915072245440000000

Offset: 1

Author

Seiichi Manyama, Nov 22 2017

Keywords

• nonn

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..50
• Eric Weisstein's World of Mathematics, Totient Function.
• Wikipedia, Euler's totient function.

Crossrefs

Column k=10 of A369291.

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).

Programs

Mathematica

Array[EulerPhi[10^# - 1]/# &, 25] (* Paolo Xausa, Jun 17 2024 *)

PARI

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