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 A136169 #8 Aug 10 2021 16:54:32
%S A136169 1,2,3,5,9,16,30,58,113,223,443,882,1760,3516,7027,14049,28093,56180,
%T A136169 112354,224702,449397,898787,1797567,3595126,7190244,14380480,
%U A136169 28760951,57521893,115043777,230087544,460175078,920350146,1840700281,3681400551
%N A136169 a(n) = 2*a(n-1) - [(n+1)/3] for n>0 with a(0) = 1.
%H A136169 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2,1,-3,2).
%F A136169 G.f.: (1 - x^2*(1+x+x^2)/(1-x^3)^2 )/(1-2*x).
%t A136169 nxt[{n_,a_}]:={n+1, 2a-Floor[(n+2)/3]}; NestList[nxt,{0,1},50][[All,2]] (* _Harvey P. Dale_, Aug 09 2021 *)
%o A136169 (PARI) {a(n)=if(n==0,1,2*a(n-1)-((n+1)\3))}
%Y A136169 Cf. A136219.
%K A136169 nonn,easy
%O A136169 0,2
%A A136169 _Paul D. Hanna_, Dec 23 2007