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 A250520 #6 Jul 23 2025 12:29:53 %S A250520 50,1180,21955,300131,3183434,27910024,212707851,1462376991, %T A250520 9314700106,56025183452,322542598187 %N A250520 Number of (n+1)X(n+1) 0..2 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing x(i,j)-x(i-1,j) in the j direction. %C A250520 Diagonal of A250527 %e A250520 Some solutions for n=3 %e A250520 ..2..1..2..1....1..1..0..0....2..2..1..1....2..1..2..0....2..0..1..0 %e A250520 ..1..0..1..0....0..0..0..0....1..1..0..0....2..1..2..1....2..1..2..2 %e A250520 ..1..1..2..1....1..1..2..2....2..2..1..1....1..1..2..2....2..1..2..2 %e A250520 ..0..0..2..1....0..1..2..2....0..2..1..2....0..1..2..2....0..1..2..2 %K A250520 nonn %O A250520 1,1 %A A250520 _R. H. Hardin_, Nov 24 2014