A295501 a(n) = phi(4^n-1), where phi is Euler's totient function (A000010).

2, 8, 36, 128, 600, 1728, 10584, 32768, 139968, 480000, 2640704, 6635520, 44717400, 132765696, 534600000, 2147483648, 11452896600, 26121388032, 183250539864, 473702400000, 2427720325632, 8834232287232, 45914084232320, 109586090557440, 656100000000000

Offset: 1

Author

Seiichi Manyama, Nov 22 2017

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 1..1128
• Eric Weisstein's World of Mathematics, Totient Function.
• Wikipedia, Euler's totient function.

Crossrefs

Cf. A000010, A053285.

phi(k^n-1): A053287 (k=2), A295500 (k=3), this sequence (k=4), A295502 (k=5), A366623 (k=6), A366635 (k=7), A366654 (k=8), A366663 (k=9), A295503 (k=10), A366685 (k=11), A366711 (k=12).

Cf. A366602, A366603, A366604, A366608.

Programs

Mathematica

EulerPhi[4^Range[30] - 1] (* Paolo Xausa, Jun 17 2024 *)

PARI

{a(n) = eulerphi(4^n-1)}

Formula

a(n) = n*A027695(n).

a(n) = A053287(2*n) = A053285(n) * A053287(n). - Max Alekseyev, Jan 07 2024