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 A269283 #7 Apr 19 2020 23:48:35 %S A269283 4,216,62748,87559668,598478857956,20680187784811380, %T A269283 3689070798270477232620,3444847181845510308844394628, %U A269283 16998439594375033474993893597991428 %N A269283 Number of n X n 0..3 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling three no more than once. %C A269283 Diagonal of A269289. %H A269283 R. H. Hardin, <a href="/A269283/b269283.txt">Table of n, a(n) for n = 1..11</a> %e A269283 Some solutions for n=3 %e A269283 ..1..0..2. .1..0..2. .1..0..0. .0..2..0. .1..0..2. .2..2..1. .3..3..1 %e A269283 ..1..2..3. .1..2..0. .3..2..2. .1..1..1. .0..0..0. .0..1..3. .1..1..0 %e A269283 ..2..2..0. .0..1..1. .2..3..1. .1..1..1. .0..0..2. .0..2..3. .0..0..0 %Y A269283 Cf. A269289. %K A269283 nonn %O A269283 1,1 %A A269283 _R. H. Hardin_, Feb 21 2016