A366639 a(n) = phi(7^n+1), where phi is Euler's totient function (A000010).

1, 4, 20, 168, 1200, 7600, 43200, 407680, 2712832, 19707408, 112560000, 945677920, 6768230400, 47530457728, 271289229120, 2096760960000, 16569393144832, 116315256993600, 597938524646400, 5699431359135360, 38890647857280000, 270061302781670400

Offset

0,2

Links

Max Alekseyev, Table of n, a(n) for n = 0..396

Formula

a(n) = A000010(A034491(n)). - Paul F. Marrero Romero, Nov 06 2023

Mathematica

EulerPhi[7^Range[0, 21] + 1] (* Paul F. Marrero Romero, Nov 05 2023 *)

Prog

(PARI) {a(n) = eulerphi(7^n+1)}

Crossrefs

Cf. A034491, A000010, A057937, A227575, A366635, A366636, A366637, A366638.

Cf. A053285, A366579, A366608, A366618, A366630, A366658, A366667, A366669, A366690, A366716.

Sequence in context: A378279 A032333 A357666 * A068965 A185672 A210438

Adjacent sequences: A366636 A366637 A366638 * A366640 A366641 A366642

Keyword

nonn

Author

Sean A. Irvine, Oct 15 2023

Status

approved