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 A173266 #9 Jan 23 2019 08:29:23
%S A173266 1,1,-1,1,-2,-1,1,-2,0,-1,1,-2,-2,0,-1,1,-2,2,0,0,-1,1,-2,-4,-2,0,0,
%T A173266 -1,1,-2,6,2,0,0,0,-1,1,-2,-10,0,-2,0,0,0,-1,1,-2,16,-4,2,0,0,0,0,-1,
%U A173266 1,-2,-26,6,0,-2,0,0,0,0,-1,1,-2,42,-2,0,2,0,0,0,0,0,-1
%N A173266 T(0,k) = 1 and T(n,k) = [x^k] (x^(n + 1) - 1)/((x - 2)*x^n + 1) for n >= 1, square array read by descending antidiagonals (n >= 0, k >= 0).
%e A173266 Square array begins:
%e A173266 n\k | 0 1 2 3 4 5 6 7 8 ...
%e A173266 --------------------------------------------
%e A173266 0 | 1 1 1 1 1 1 1 1 1 ...
%e A173266 1 | -1 -2 -2 -2 -2 -2 -2 -2 -2 ...
%e A173266 2 | -1 0 -2 2 -4 6 -10 16 -26 ...
%e A173266 3 | -1 0 0 -2 2 0 -4 6 -2 ...
%e A173266 4 | -1 0 0 0 -2 2 0 0 -4 ...
%e A173266 5 | -1 0 0 0 0 -2 2 0 0 ...
%e A173266 6 | -1 0 0 0 0 0 -2 2 0 ...
%e A173266 7 | -1 0 0 0 0 0 0 -2 2 ...
%e A173266 8 | -1 0 0 0 0 0 0 0 -2 ...
%e A173266 ...
%t A173266 p[x_, n_] = If[n == 0, 1/(1 - x), (Sum[x^i, {i, 0, n}])/(x^n - Sum[x^i, {i, 0, n - 1}])];
%t A173266 a = Table[Table[SeriesCoefficient[Series[p[x, n], {x, 0, 50}], m], {m, 0, 20}], {n, 0, 20}];
%t A173266 Flatten[Table[Table[a[[m, n - m + 1]], {m, 1, n}], {n, 1, 10}]]
%o A173266 (Maxima) (kk : 50, nn : 15)$
%o A173266 gf(n) := taylor(if n = 0 then 1/(1 - x) else (x^(n + 1) - 1)/((x - 2)*x^n + 1), x, 0, kk)$
%o A173266 T(n, k) := ratcoef(gf(n), x, k)$
%o A173266 create_list(T(k, n - k), n, 0, nn, k, 0, n);
%o A173266 /* _Franck Maminirina Ramaharo_, Jan 23 2019 */
%Y A173266 Cf. A173264, A173265.
%K A173266 sign,easy,tabl
%O A173266 0,5
%A A173266 _Roger L. Bagula_, Feb 14 2010
%E A173266 Edited by _Franck Maminirina Ramaharo_, Jan 23 2019