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

1,1

Links

Max Alekseyev, Table of n, a(n) for n = 1..352

Eric W. Weisstein, MathWorld: Totient Function

Wikipedia, Euler's totient function

Formula

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

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

Mathematica

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

Prog

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

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.

Sequence in context: A322441 A186674 A186672 * A106259 A085364 A228484

Adjacent sequences: A295500 A295501 A295502 * A295504 A295505 A295506

Keyword

nonn

Author

Seiichi Manyama, Nov 22 2017

Status

approved