A295503 a(n) = phi(10^n-1), where phi is Euler's totient function (A000010).

6, 60, 648, 6000, 64800, 466560, 6637344, 58752000, 648646704, 5890320000, 66663457344, 461894400000, 6458084523072, 60339430569600, 610154104320000, 5529599115264000, 66666634474902192, 441994921381739520, 6666666666666666660, 58301444908800000000

Offset: 1

Author

Seiichi Manyama, Nov 22 2017

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 1..352
• Eric W. Weisstein, MathWorld: Totient Function
• Wikipedia, Euler's totient function

Crossrefs

phi(k^n-1): A053287 (k=2), A295500 (k=3), A295501 (k=4), A295502 (k=5), A366623 (k=6), A366635 (k=7), A366654 (k=8), A366663 (k=9), this sequence (k=10), A366685 (k=11), A366711 (k=12).

Cf. A000010, A002283.

Programs

Mathematica

Array[ EulerPhi[10^# - 1] &, 20] (* Robert G. Wilson v, Nov 22 2017 *)

PARI

{a(n) = eulerphi(10^n-1)}

Formula

a(n) = n*A295497(n).

a(n) = A000010(A002283(n)). - Michel Marcus, Nov 25 2017