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 A269046 #7 Apr 19 2020 23:46:30 %S A269046 3,42,594,24192,1643376,242861616,71430596250,43961616939276, %T A269046 56121206116838532,149312689805356303800,836315757545942679945480, %U A269046 9777884421682321788379713444,242268002268280142077867206348378 %N A269046 Number of n X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two not more than once. %C A269046 Diagonal of A269052. %H A269046 R. H. Hardin, <a href="/A269046/b269046.txt">Table of n, a(n) for n = 1..14</a> %e A269046 Some solutions for n=4 %e A269046 ..2..0..1..2. .1..2..1..2. .0..2..1..0. .2..2..2..2. .0..2..1..2 %e A269046 ..1..2..1..0. .1..2..1..0. .1..0..1..0. .1..1..2..2. .1..0..1..2 %e A269046 ..1..2..1..0. .1..0..1..0. .0..0..0..0. .2..2..2..1. .0..0..1..0 %e A269046 ..1..0..1..0. .1..2..0..0. .0..0..0..1. .1..2..2..2. .0..0..1..0 %Y A269046 Cf. A269052. %K A269046 nonn %O A269046 1,1 %A A269046 _R. H. Hardin_, Feb 18 2016