A366608 a(n) = phi(4^n+1), where phi is Euler's totient function (A000010).

1, 4, 16, 48, 256, 800, 3840, 12544, 65536, 186624, 986880, 3345408, 16515072, 52306176, 252645120, 760320000, 4288266240, 13628740608, 64258375680, 218462552064, 1095233372160, 3105655160832, 16510446886912, 56000724240384, 280012271910912, 869940000000000

Offset

0,2

Links

Max Alekseyev, Table of n, a(n) for n = 0..561

Formula

a(n) = A053285(2*n). - Max Alekseyev, Jan 08 2024

Mathematica

EulerPhi[4^Range[0, 30]+1] (* Paolo Xausa, Oct 14 2023 *)

Prog

(PARI) {a(n) = eulerphi(4^n+1)}
(Python)
from sympy import totient
def A366608(n): return totient((1<<(n<<1))+1) # Chai Wah Wu, Oct 14 2023

Crossrefs

Cf. A000010, A052539, A057940, A274903, A295501, A366605, A366606, A366607, A366609.

Cf. A053285, A366579, A366618, A366630, A366639, A366658, A366667, A366669, A366690, A366716.

Sequence in context: A119003 A220329 A222387 * A222936 A370019 A119005

Adjacent sequences: A366605 A366606 A366607 * A366609 A366610 A366611

Keyword

nonn

Author

Sean A. Irvine, Oct 14 2023

Status

approved