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 A229373 #8 May 03 2021 13:33:56 %S A229373 3,30,956,78690,20014278,13999334726,29757371834046, %T A229373 174511010613631514,3123774881474924676470, %U A229373 153541601581149110702908096,23150533101205838897343355257558,9547382122506738591063952302014235288 %N A229373 Number of n X n 0..2 arrays avoiding 11 horizontally, 22 vertically and 00 diagonally or antidiagonally. %C A229373 Diagonal of A229380. %H A229373 R. H. Hardin, <a href="/A229373/b229373.txt">Table of n, a(n) for n = 1..13</a> %e A229373 Some solutions for n=4 %e A229373 ..1..0..1..0....2..0..0..2....2..0..2..1....1..2..2..1....1..2..1..2 %e A229373 ..1..0..1..0....1..2..2..1....1..0..1..2....2..0..1..0....0..0..0..0 %e A229373 ..2..0..1..2....1..0..1..2....1..0..1..0....1..0..2..0....2..1..2..1 %e A229373 ..1..2..2..1....1..2..1..0....2..0..1..2....1..0..1..2....0..0..0..2 %Y A229373 Cf. A229380. %K A229373 nonn %O A229373 1,1 %A A229373 _R. H. Hardin_ Sep 21 2013