A366667 a(n) = phi(9^n+1), where phi is Euler's totient function (A000010).

1, 4, 40, 288, 3072, 23600, 259200, 1847104, 21523360, 152845056, 1700870400, 12550120000, 130459631616, 997562438080, 11159367815680, 81159501312000, 926510094425920, 6670865700716544, 73205598106368000, 540340585126398016, 5691215305506816000

Offset: 0

Author

Sean A. Irvine, Oct 15 2023

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 0..345

Crossrefs

Cf. A062396, A000010, A366663, A366664, A366665, A366666.

Cf. A053285, A366579, A366608, A366618, A366630, A366639, A366658, A366669, A366690, A366716.

Programs

Mathematica

EulerPhi[9^Range[0, 20] + 1] (* Paul F. Marrero Romero, Nov 04 2023 *)

PARI

{a(n) = eulerphi(9^n+1)}

Formula

a(n) = A000010(A062396(n)). - Paul F. Marrero Romero, Nov 04 2023

a(n) = A366579(2*n). - Max Alekseyev, Jan 08 2024