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 A046637 Number of cubic residues mod 9^n. 0

%I

%S 1,3,21,169,1515,13629,122641,1103763,9933861,89404729,804642555,

%T 7241782989,65176046881,586584421923,5279259797301,47513338175689,

%U 427620043581195,3848580392230749,34637223530076721,311735011770690483

%N Number of cubic residues mod 9^n.

%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (9,0,1,-9)

%F a(n) = A046530(9^n) = A046631(2n). G.f. ( 1-6*x-6*x^2-21*x^3 ) / ( (x-1)*(9*x-1)*(1+x+x^2) ). - _R. J. Mathar_, Feb 28 2011

%F If n>=1, a(n) = 9*a(n-1) -6 if n is not a multiple of 3, otherwise a(n) = 9*a(n-1) -20. - _Vincenzo Librandi_, Mar 18 2011

%t LinearRecurrence[{9,0,1,-9},{1,3,21,169},30] (* _Harvey P. Dale_, Oct 09 2017 *)

%K nonn,easy

%O 0,2

%A _David W. Wilson_

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Last modified February 27 22:47 EST 2020. Contains 332312 sequences. (Running on oeis4.)