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A295496
a(n) = phi(6^n-1)/n, where phi is Euler's totient function (A000010).
5
4, 12, 56, 216, 1240, 5040, 31992, 139968, 828576, 3720000, 25238048, 104509440, 803499840, 3687014016, 24373440000, 110630707200, 790546192128, 3463116249600, 25522921047520, 108957312000000, 816244048599840, 3924124012353600, 26682733370563200
OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Totient Function.
MATHEMATICA
Array[EulerPhi[6^# - 1]/# &, 25] (* Paolo Xausa, Jun 17 2024 *)
PROG
(PARI) {a(n) = eulerphi(6^n-1)/n}
CROSSREFS
Column k=6 of A369291.
phi(k^n-1)/n: A011260 (k=2), A027385 (k=3), A027695 (k=4), A027741 (k=5), this sequence (k=6), A027743 (k=7), A027744 (k=8), A027745 (k=9), A295497 (k=10), A319166 (k=11).
Sequence in context: A179607 A149422 A149423 * A164575 A124004 A243785
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 22 2017
STATUS
approved