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A366669
a(n) = phi(10^n+1), where phi is Euler's totient function (A000010).
8
1, 10, 100, 720, 9792, 90900, 990000, 9090900, 94117632, 681410880, 9897840000, 86925373920, 979102080000, 9080325951840, 95255567232000, 712493107200000, 9926748531589120, 90004044661864320, 989999010000000000, 9090909090909090900, 97910150554895155200
OFFSET
0,2
LINKS
FORMULA
a(n) = A000010(A062397(n)). - Paul F. Marrero Romero, Nov 10 2023
MATHEMATICA
EulerPhi[10^Range[0, 20] + 1] (* Paul F. Marrero Romero, Nov 10 2023 *)
PROG
(PARI) {a(n) = eulerphi(10^n+1)}
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 15 2023
STATUS
approved