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 A143432 #21 Nov 20 2023 00:04:00
%S A143432 1,1,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,
%T A143432 0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,
%U A143432 2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2,2,0,0,2
%N A143432 Ultimately period 4 sequence [ 2, 2, 0, 0, ...] with a(0) = a(1) = 1.
%H A143432 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,-1,1)
%F A143432 Euler transform of length 8 sequence [ 1, -1, 0, 2, 0, 0, 0, -1].
%F A143432 a(4*n + 2) = a(4*n + 3) = 0. a(4*n) = a(4*n + 1) = 2 unless n < 1.
%F A143432 G.f.: (1 + x^4) / ((1 - x) * (1 + x^2)).
%F A143432 a(n) = ((n+2) mod 4) - (n mod 2) - floor(3/(n+2)). - _Wesley Ivan Hurt_, Jun 30 2013
%t A143432 PadRight[{1,1},120,{2,2,0,0}] (* _Harvey P. Dale_, Feb 13 2016 *)
%o A143432 (PARI) {a(n) = if(n<0, 0, n = n\2; if( n%2, 0, (n>1)+1 ))}
%Y A143432 Convolution inverse of A143431.
%K A143432 nonn,easy
%O A143432 0,5
%A A143432 _Michael Somos_, Aug 14 2008, Sep 18 2008