This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A046637 #21 Mar 27 2024 13:29:24
%S A046637 1,3,21,169,1515,13629,122641,1103763,9933861,89404729,804642555,
%T A046637 7241782989,65176046881,586584421923,5279259797301,47513338175689,
%U A046637 427620043581195,3848580392230749,34637223530076721,311735011770690483
%N A046637 Number of cubic residues mod 9^n.
%H A046637 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (9,0,1,-9)
%F A046637 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 A046637 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 A046637 LinearRecurrence[{9,0,1,-9},{1,3,21,169},30] (* _Harvey P. Dale_, Oct 09 2017 *)
%K A046637 nonn,easy
%O A046637 0,2
%A A046637 _David W. Wilson_