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 A221325 #6 Jun 02 2025 08:16:05 %S A221325 41,6328,1010078,162430981,26135748494,4205264399891,676612123702617, %T A221325 108863121975329470,17515379016294357354,2818106397041464685615, %U A221325 453413942381102088419081,72951161699753445110986111 %N A221325 Number of nX5 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, with no occupancy greater than 2. %C A221325 Column 5 of A221328 %H A221325 R. H. Hardin, <a href="/A221325/b221325.txt">Table of n, a(n) for n = 1..77</a> %e A221325 Some solutions for n=3 %e A221325 ..0..1..2..2..1....0..2..1..2..1....0..1..2..2..1....0..1..2..1..1 %e A221325 ..0..2..0..1..2....0..0..2..0..2....0..2..1..2..0....0..2..0..2..1 %e A221325 ..0..0..1..1..2....2..2..0..1..0....0..2..0..0..2....1..1..1..1..1 %K A221325 nonn %O A221325 1,1 %A A221325 _R. H. Hardin_ Jan 11 2013