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 A153509 #18 Dec 12 2023 08:10:28
%S A153509 6,6,6,3,3,3,0,0,0,6,6,6,3,3,3,0,0,0,6,6,6,3,3,3,0,0,0,6,6,6,3,3,3,0,
%T A153509 0,0,6,6,6,3,3,3,0,0,0,6,6,6,3,3,3,0,0,0,6,6,6,3,3,3,0,0,0,6,6,6,3,3,
%U A153509 3,0,0,0,6,6,6,3,3,3,0,0,0,6,6,6,3,3,3,0,0,0,6,6,6,3,3,3,0,0,0,6,6,6,3,3,3
%N A153509 Period 9: repeat [6, 6, 6, 3, 3, 3, 0, 0, 0].
%H A153509 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,-1,1,0,-1,1).
%F A153509 G.f.: 3*(2+x^3)/((1-x)*(1+x^3+x^6)). - _R. J. Mathar_, Jan 21 2009
%F A153509 a(n) = 3*((3-floor((n+3)/3)) mod 3). - _Wesley Ivan Hurt_, Apr 27 2020
%t A153509 PadRight[{},9*12,{6,6,6,3,3,3,0,0,0}] (* _Harvey P. Dale_, Dec 17 2012 *)
%o A153509 (PARI) a(n)=[6,6,6,3,3,3,0,0,0][n%9+1] \\ _Charles R Greathouse IV_, Jul 13 2016
%Y A153509 Cf. A130851.
%K A153509 nonn,easy
%O A153509 0,1
%A A153509 _Paul Curtz_, Dec 28 2008
%E A153509 More periods from _R. J. Mathar_, Jan 21 2009