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A366618
a(n) = phi(5^n+1), where phi is Euler's totient function (A000010).
10
1, 2, 12, 36, 312, 1040, 7200, 25088, 183808, 557928, 4396800, 15333120, 121680000, 406812744, 2817007200, 8558784000, 76264519680, 254230063200, 1710194342400, 6349120596480, 47334145996800, 127169887444992, 1088029470747648, 3889097389599864
OFFSET
0,2
LINKS
PROG
(PARI) {a(n) = eulerphi(5^n+1)}
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 14 2023
STATUS
approved