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 A250684 #6 Jul 23 2025 12:41:23 %S A250684 104,2920,74631,1670016,31728758,523260542,7662909389 %N A250684 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 A250684 Diagonal of A250691 %e A250684 Some solutions for n=3 %e A250684 ..3..2..1..1....3..3..1..0....2..0..0..0....3..3..2..0....1..3..1..0 %e A250684 ..2..1..0..0....3..3..1..0....2..0..0..0....3..3..2..2....1..3..2..1 %e A250684 ..2..1..0..0....3..3..1..1....3..1..1..1....2..2..1..1....0..2..1..0 %e A250684 ..1..2..3..3....2..2..0..2....2..3..3..3....1..3..3..3....0..2..1..3 %K A250684 nonn %O A250684 1,1 %A A250684 _R. H. Hardin_, Nov 26 2014