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 A233151 #10 Jun 25 2024 13:13:21 %S A233151 3,24,432,17496,1658232,367125912,191184793128,234385100907480, %T A233151 677856222475099560,4627785508146660629232,74650443539914896103253016, %U A233151 2846446729148572555427535908448,256684477494955879310882598953790768 %N A233151 Number of n X n 0..2 arrays with no element x(i,j) adjacent to value 2-x(i,j) horizontally or antidiagonally. %H A233151 R. H. Hardin, <a href="/A233151/b233151.txt">Table of n, a(n) for n = 1..17</a> %e A233151 Some solutions for n=4: %e A233151 ..2..2..1..2....1..0..1..2....1..0..1..2....0..1..0..0....0..0..1..2 %e A233151 ..1..0..1..0....1..0..1..0....1..2..2..1....0..0..1..0....1..2..1..0 %e A233151 ..0..0..0..0....0..0..0..1....1..2..2..1....0..0..1..2....1..0..0..0 %e A233151 ..1..0..1..2....1..0..0..1....1..2..2..1....0..0..1..0....1..0..0..1 %Y A233151 Diagonal of A233155. %K A233151 nonn %O A233151 1,1 %A A233151 _R. H. Hardin_, Dec 05 2013