A295500 a(n) = phi(3^n-1), where phi is Euler's totient function (A000010).

1, 4, 12, 32, 110, 288, 1092, 2560, 9072, 26400, 84700, 165888, 797160, 2384928, 6019200, 15728640, 64533700, 141087744, 580765248, 1246080000, 4823425152, 14758128000, 46070066188, 85996339200, 385087175000, 1270928131200, 3474144608256, 8810420097024

Offset: 1

Author

Seiichi Manyama, Nov 22 2017

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 1..690
• Eric Weisstein's World of Mathematics, Totient Function
• Wikipedia, Euler's totient function

Crossrefs

Cf. A000010, A024023, A027385.

phi(k^n-1): A053287 (k=2), this sequence (k=3), A295501 (k=4), A295502 (k=5), A366623 (k=6), A366635 (k=7), A366654 (k=8), A366663 (k=9), A295503 (k=10), A366685 (k=11), A366711 (k=12).

Programs

Mathematica

EulerPhi[3^Range[30] - 1] (* Paolo Xausa, Jun 18 2024 *)

PARI

{a(n) = eulerphi(3^n-1)}

Formula

a(n) = n*A027385(n).

a(n) = A000010(A024023(n)). - Michel Marcus, Jun 18 2024