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Number of primitive polynomials of degree n over GF(9).
5

%I #12 Jun 17 2024 18:36:11

%S 1,4,16,96,640,5280,27648,340704,1966080,15676416,124608000,

%T 1341648000,7166361600,97763702400,629315721216,4680529920000,

%U 42316647628800,483414202656000,2396062681399296,35513562609100800,211942058803200000,2006922093666287616,16837843397760000000

%N Number of primitive polynomials of degree n over GF(9).

%H Andrew Howroyd, <a href="/A027745/b027745.txt">Table of n, a(n) for n = 0..100</a>

%p with(numtheory): seq(`if`(n=0, 1, phi(9^n-1)/n), n=0..22);

%t Join[{1}, Array[EulerPhi[9^# - 1]/# &, 25]] (* _Paolo Xausa_, Jun 17 2024 *)

%o (PARI) a(n) = if(n==0, 1, eulerphi(9^n-1)/n) \\ _Andrew Howroyd_, Feb 01 2024

%Y Column k=9 of A369291.

%K nonn

%O 0,2

%A _N. J. A. Sloane_

%E a(20) onwards from _Andrew Howroyd_, Feb 01 2024