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 A059227 #12 Dec 30 2024 17:30:17
%S A059227 1,1,4,18,94,544,3370,21878,146924,1012222,7114218,50808592,367669254,
%T A059227 2689974234,19864822564,147875395930,1108469655350,8359790718480,
%U A059227 63387403235682,482935966313310,3695204342149004,28383451250732662
%N A059227 Last entry in n-th row of triangle defined in A059226.
%H A059227 G. C. Greubel, <a href="/A059227/b059227.txt">Table of n, a(n) for n = 0..250</a>
%H A059227 <a href="/index/Bo#boustrophedon">Index entries for sequences related to boustrophedon transform</a>
%t A059227 T[i_, j_] := T[i, j] = Module[{r, s, t1}, If[i == 0 && j == 0,Return[1]];
%t A059227 If[j == 0, Return[0]]; t1 = T[i, j - 1]; For[r = 0, r <= i - j, r++,
%t A059227 For[s = 0, s <= j, s++, If[r + s != i, t1 = t1 + T[r + s, s]]]];
%t A059227 Return[t1]]; Table[T[n, n], {n, 0, 25}] (* _G. C. Greubel_, Jan 03 2017 *)
%t A059227 Join[{1}, CoefficientList[Nest[1+(3x-x^2)#+(x-x^2)#^2&, 1+O[x], 20], x]] (* _Oliver Seipel_, Dec 28 2024 *)
%K A059227 nonn
%O A059227 0,3
%A A059227 _N. J. A. Sloane_, Jan 19 2001