A366618 a(n) = phi(5^n+1), where phi is Euler's totient function (A000010).

1, 2, 12, 36, 312, 1040, 7200, 25088, 183808, 557928, 4396800, 15333120, 121680000, 406812744, 2817007200, 8558784000, 76264519680, 254230063200, 1710194342400, 6349120596480, 47334145996800, 127169887444992, 1088029470747648, 3889097389599864

Offset: 0

Author

Sean A. Irvine, Oct 14 2023

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 0..471

Crossrefs

Cf. A000010, A034474, A057939, A074478, A295502, A366615, A366616, A366617.

Cf. A053285, A366579, A366608, A366630, A366639, A366658, A366667, A366669, A366690, A366716.

Programs

Mathematica

EulerPhi[5^Range[0,30]+1] (* Harvey P. Dale, Jun 07 2025 *)

PARI

{a(n) = eulerphi(5^n+1)}