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 A252977 #8 Jul 23 2025 13:49:44 %S A252977 0,0,1,68,4657,432842,60650883,13458882036,4857082197177, %T A252977 2895119784219358,2877300288177184239,4796057029604523514392, %U A252977 13457301734652492685623300,63707500883584152928303777296 %N A252977 Number of n X n nonnegative integer arrays with upper left 0 and lower right its king-move distance away minus 2 and every value increasing by 0 or 1 with every step right, diagonally se or down. %C A252977 Diagonal of A252983 %H A252977 R. H. Hardin, <a href="/A252977/b252977.txt">Table of n, a(n) for n = 1..15</a> %e A252977 Some solutions for n=4 %e A252977 ..0..0..0..1....0..0..0..0....0..0..0..1....0..0..0..0....0..0..1..1 %e A252977 ..0..0..0..1....0..0..0..1....1..1..1..1....0..0..0..0....0..0..1..1 %e A252977 ..0..1..1..1....0..0..1..1....1..1..1..1....0..0..0..0....0..1..1..1 %e A252977 ..1..1..1..1....1..1..1..1....1..1..1..1....1..1..1..1....1..1..1..1 %K A252977 nonn %O A252977 1,4 %A A252977 _R. H. Hardin_, Dec 25 2014