OFFSET
1,1
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..420
FORMULA
MATHEMATICA
EulerPhi[6^Range[22] - 1] (* Paul F. Marrero Romero, Oct 23 2023 *)
PROG
(PARI) {a(n) = eulerphi(6^n-1)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 14 2023
STATUS
approved