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 A232949 #8 Jul 23 2025 07:45:31 %S A232949 1,21,1881,685251,1074244299,7168373617095,205030957086979647, %T A232949 25121788915317351455997,13201474923932116066095060171, %U A232949 29758989052767328125373420316820645 %N A232949 Number of n X n 0..3 arrays with no element x(i,j) adjacent to value 3-x(i,j) horizontally, diagonally or antidiagonally, and top left element zero. %C A232949 Diagonal of A232955 %H A232949 R. H. Hardin, <a href="/A232949/b232949.txt">Table of n, a(n) for n = 1..11</a> %e A232949 Some solutions for n=3 %e A232949 ..0..2..0....0..1..0....0..1..0....0..1..0....0..2..0....0..0..1....0..1..3 %e A232949 ..3..2..3....3..2..3....1..0..0....1..0..1....3..2..3....0..0..1....1..1..1 %e A232949 ..2..3..2....3..1..0....0..0..2....2..3..1....3..2..0....0..1..0....0..0..1 %K A232949 nonn %O A232949 1,2 %A A232949 _R. H. Hardin_, Dec 02 2013