A366635 a(n) = phi(7^n-1), where phi is Euler's totient function (A000010).

2, 16, 108, 640, 5600, 36288, 264992, 1536000, 12387168, 85120000, 658519752, 3135283200, 32296336800, 216063877120, 1450340640000, 8333819904000, 77537969371008, 488237947481088, 3790563394976072, 19162214400000000, 170264753751665664, 1245495178700551680

Offset: 1

Author

Sean A. Irvine, Oct 15 2023

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 1..388

Crossrefs

phi(k^n-1): A053287 (k=2), A295500 (k=3), A295501 (k=4), A295502 (k=5), A366623 (k=6), this sequence (k=7), A366654 (k=8), A366663 (k=9), A295503 (k=10), A366685 (k=11), A366711 (k=12).

Cf. A000010, A024075, A366632, A366633, A366634.

Programs

Mathematica

EulerPhi[7^Range[30] - 1] (* Wesley Ivan Hurt, Oct 15 2023 *)

PARI

{a(n) = eulerphi(7^n-1)}