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 A250668 #6 Apr 24 2021 09:22:33 %S A250668 104,5154,388916,41503790,5803025694,1009432228498,210335029800118 %N A250668 Number of (n+1) X (n+1) 0..3 arrays with nondecreasing x(i,j)+x(i,j-1) in the i direction and nondecreasing absolute value of x(i,j)-x(i-1,j) in the j direction. %C A250668 Diagonal of A250676. %e A250668 Some solutions for n=2 %e A250668 ..1..1..1....1..2..0....2..2..1....0..2..0....3..0..3....1..0..0....1..0..2 %e A250668 ..2..2..2....1..2..3....2..3..3....0..2..1....1..3..0....2..2..2....0..1..3 %e A250668 ..2..2..2....1..2..3....2..3..3....1..1..3....3..1..3....2..2..2....2..3..1 %Y A250668 Cf. A250676. %K A250668 nonn %O A250668 1,1 %A A250668 _R. H. Hardin_, Nov 26 2014