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A295503
a(n) = phi(10^n-1), where phi is Euler's totient function (A000010).
12
6, 60, 648, 6000, 64800, 466560, 6637344, 58752000, 648646704, 5890320000, 66663457344, 461894400000, 6458084523072, 60339430569600, 610154104320000, 5529599115264000, 66666634474902192, 441994921381739520, 6666666666666666660, 58301444908800000000
OFFSET
1,1
LINKS
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).
Sequence in context: A322441 A186674 A186672 * A106259 A085364 A228484
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 22 2017
STATUS
approved