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 A216220 #7 Mar 14 2013 20:50:03
%S A216220 1,1,1,1,2,0,1,3,2,0,0,4,5,0,0,0,4,9,5,0,0,0,0,13,14,0,0,0,0,0,13,27,
%T A216220 14,0,0,0,0,0,0,40,41,0,0,0,0,0,0,0,40,81,41,0,0,0,0,0,0,0,0,121,122,
%U A216220 0,0,0,0,0
%N A216220 Square array T, read by antidiagonals: T(n,k) = 0 if n-k>=2 or if k-n>=4, T(1,0) = T(0,0) = T(0,1) = T(0,2) = T(0,3) = 1, T(n,k) = T(n-1,k) + T(n,k-1).
%C A216220 T(0,2), T(1,1), T(1,2), T(1,3), ... T(n,n), T(n,n+1), T(n,n+2), ... is the sequence A140298.
%F A216220 T(n,n) = T(n+1,n) = A007051(n).
%F A216220 T(n,n+1) = 3^n = A000244(n).
%F A216220 T(n,n+2) = T(n,n+3) = A003462(n+1).
%F A216220 Sum_{k, 0<=k<=n} T(n-k,k) = A038754(n).
%e A216220 Square array begins:
%e A216220 1, 1, 1, 1, 0, 0, 0, 0, 0, ...
%e A216220 1, 2, 3, 4, 4, 0, 0, 0, 0, ...
%e A216220 0, 2, 5, 9, 13, 13, 0, 0, 0, ...
%e A216220 0, 0, 5, 14, 27, 40, 40, 0, 0, ...
%e A216220 0, 0, 0, 14, 41, 81, 121, 121, 0, ...
%e A216220 ...
%Y A216220 Cf. A000244, A003462, A007051, A038754,
%K A216220 nonn,tabl
%O A216220 0,5
%A A216220 _Philippe Deléham_, Mar 13 2013