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 A252830 #8 Jul 23 2025 13:40:59 %S A252830 1,5,44,493,6068,78674,1056756,14564701,204666202,2919462498, %T A252830 42143180174,614251526864,9024782449736,133489812361806, %U A252830 1985873221687284,29689739907869581,445797648515664064,6719243690952576928 %N A252830 Number of n X n nonnegative integer arrays with upper left 0 and every value within 2 of its king move distance from the upper left and every value increasing by 0 or 1 with every step right, diagonally se or down. %C A252830 Diagonal of A252836 %H A252830 R. H. Hardin, <a href="/A252830/b252830.txt">Table of n, a(n) for n = 1..29</a> %e A252830 Some solutions for n=4 %e A252830 ..0..0..1..2....0..0..1..1....0..0..1..1....0..0..1..1....0..0..0..1 %e A252830 ..1..1..1..2....1..1..1..1....1..1..1..2....1..1..1..1....1..1..1..1 %e A252830 ..1..1..2..2....1..1..1..1....1..1..1..2....1..2..2..2....1..1..1..1 %e A252830 ..2..2..2..2....2..2..2..2....1..2..2..2....1..2..2..3....2..2..2..2 %K A252830 nonn %O A252830 1,2 %A A252830 _R. H. Hardin_, Dec 22 2014