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 A219877 #9 Mar 28 2025 17:08:21 %S A219877 3,7,47,621,14536,764027,113313853 %N A219877 Number of n X n arrays of the minimum value of corresponding elements and their horizontal, diagonal or antidiagonal neighbors in a random, but sorted with lexicographically nondecreasing rows and nonincreasing columns, 0..2 n X n array. %e A219877 Some solutions for n=3: %e A219877 ..0..0..0....1..0..1....2..2..2....2..0..0....2..0..0....1..1..1....1..0..1 %e A219877 ..0..0..0....1..0..0....2..2..2....2..0..1....2..0..0....1..1..1....1..0..0 %e A219877 ..0..1..0....2..0..2....2..2..2....2..1..1....2..0..2....2..1..1....2..0..0 %Y A219877 Diagonal of A219883. %K A219877 nonn,more %O A219877 1,1 %A A219877 _R. H. Hardin_, Nov 30 2012