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 A021337 #32 Aug 11 2025 16:30:38
%S A021337 0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,
%T A021337 0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,
%U A021337 3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3,0,0,3
%N A021337 Decimal expansion of 1/333.
%H A021337 Vincenzo Librandi, <a href="/A021337/b021337.txt">Table of n, a(n) for n = 0..1000</a>
%H A021337 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,1).
%F A021337 G.f.: 3*x^2/(1 - x^3). - _Chai Wah Wu_, Jun 21 2016
%F A021337 From _Wesley Ivan Hurt_, Jul 02 2016: (Start)
%F A021337 a(n) = a(n-3) for n>2.
%F A021337 a(n) = 1 - cos(2*n*Pi/3) - sqrt(3)*sin(2*n*Pi/3).
%F A021337 a(n) = 3*(1 - sgn((n+1) mod 3)).
%F A021337 a(n) = 1 + (n mod 3) - ((n+1) mod 3). (End)
%e A021337 0.00300300300300300300300300300300300300300300300300...
%p A021337 seq(op([0, 0, 3]), n=0..50); # _Wesley Ivan Hurt_, Jul 02 2016
%t A021337 PadLeft[First@#, Abs@Last@# + Length@First@#]&@RealDigits[N[1/333, 100]] (* _Vincenzo Librandi_, Jun 22 2016 *)
%t A021337 PadRight[{}, 100, {0, 0, 3}] (* _Wesley Ivan Hurt_, Jul 02 2016 *)
%t A021337 realDigitsRecip[333] (* The realDigitsRecip program is at A021200 *) (* _Harvey P. Dale_, Apr 10 2025 *)
%o A021337 (Magma) &cat [[0, 0, 3]^^30]; // _Wesley Ivan Hurt_, Jul 02 2016
%K A021337 nonn,cons,easy
%O A021337 0,3
%A A021337 _N. J. A. Sloane_