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

1,1

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.

Mathematica

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

Prog

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

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).

Sequence in context: A231209 A073087 A214822 * A298457 A208942 A209070

Adjacent sequences: A295494 A295495 A295496 * A295498 A295499 A295500

Keyword

nonn

Author

Seiichi Manyama, Nov 22 2017

Status

approved