A295496 a(n) = phi(6^n-1)/n, where phi is Euler's totient function (A000010).

4, 12, 56, 216, 1240, 5040, 31992, 139968, 828576, 3720000, 25238048, 104509440, 803499840, 3687014016, 24373440000, 110630707200, 790546192128, 3463116249600, 25522921047520, 108957312000000, 816244048599840, 3924124012353600, 26682733370563200

Offset: 1

Author

Seiichi Manyama, Nov 22 2017

Keywords

• nonn

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..100
• Eric Weisstein's World of Mathematics, Totient Function.
• Wikipedia, Euler's totient function.

Crossrefs

Column k=6 of A369291.

phi(k^n-1)/n: A011260 (k=2), A027385 (k=3), A027695 (k=4), A027741 (k=5), this sequence (k=6), A027743 (k=7), A027744 (k=8), A027745 (k=9), A295497 (k=10), A319166 (k=11).

Programs

Mathematica

Array[EulerPhi[6^# - 1]/# &, 25] (* Paolo Xausa, Jun 17 2024 *)

PARI

{a(n) = eulerphi(6^n-1)/n}