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A366635
a(n) = phi(7^n-1), where phi is Euler's totient function (A000010).
14
2, 16, 108, 640, 5600, 36288, 264992, 1536000, 12387168, 85120000, 658519752, 3135283200, 32296336800, 216063877120, 1450340640000, 8333819904000, 77537969371008, 488237947481088, 3790563394976072, 19162214400000000, 170264753751665664, 1245495178700551680
OFFSET
1,1
LINKS
MATHEMATICA
EulerPhi[7^Range[30] - 1] (* Wesley Ivan Hurt, Oct 15 2023 *)
PROG
(PARI) {a(n) = eulerphi(7^n-1)}
CROSSREFS
phi(k^n-1): A053287 (k=2), A295500 (k=3), A295501 (k=4), A295502 (k=5), A366623 (k=6), this sequence (k=7), A366654 (k=8), A366663 (k=9), A295503 (k=10), A366685 (k=11), A366711 (k=12).
Sequence in context: A009619 A012024 A349008 * A193217 A329550 A208137
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 15 2023
STATUS
approved