A366663 a(n) = phi(9^n-1), where phi is Euler's totient function (A000010).

4, 32, 288, 2560, 26400, 165888, 2384928, 15728640, 141087744, 1246080000, 14758128000, 85996339200, 1270928131200, 8810420097024, 70207948800000, 677066362060800, 8218041445152000, 43129128265187328, 674757689572915200, 4238841176064000000

Offset

1,1

Links

Max Alekseyev, Table of n, a(n) for n = 1..690

Formula

a(n) = A295500(2*n) = 2 * A295500(n) * A366579(n). - Max Alekseyev, Jan 07 2024

Mathematica

EulerPhi[9^Range[30] - 1]

Prog

(PARI) {a(n) = eulerphi(9^n-1)}

Crossrefs

phi(k^n-1): A053287 (k=2), A295500 (k=3), A295501 (k=4), A295502 (k=5), A366623 (k=6), A366635 (k=7), A366654 (k=8), this sequence (k=9), A295503 (k=10), A366685 (k=11), A366711 (k=12).

Cf. A000010, A024101, A057952, A366660, A366661, A366662, A366667.

Sequence in context: A199566 A370160 A372464 * A110901 A295538 A256183

Adjacent sequences: A366660 A366661 A366662 * A366664 A366665 A366666

Keyword

nonn

Author

Sean A. Irvine, Oct 15 2023

Status

approved