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A366667
a(n) = phi(9^n+1), where phi is Euler's totient function (A000010).
11
1, 4, 40, 288, 3072, 23600, 259200, 1847104, 21523360, 152845056, 1700870400, 12550120000, 130459631616, 997562438080, 11159367815680, 81159501312000, 926510094425920, 6670865700716544, 73205598106368000, 540340585126398016, 5691215305506816000
OFFSET
0,2
LINKS
FORMULA
a(n) = A000010(A062396(n)). - Paul F. Marrero Romero, Nov 04 2023
a(n) = A366579(2*n). - Max Alekseyev, Jan 08 2024
MATHEMATICA
EulerPhi[9^Range[0, 20] + 1] (* Paul F. Marrero Romero, Nov 04 2023 *)
PROG
(PARI) {a(n) = eulerphi(9^n+1)}
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 15 2023
STATUS
approved