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 A268767 #7 Apr 19 2020 23:43:05 %S A268767 0,12,112,2296,64112,3104544,255353744,36091542548,8990276037592, %T A268767 3911658481295924,3022669494445395808,4128305052223833006600, %U A268767 10045914708457218016317000,43496963453603913793217952196 %N A268767 Number of n X n 0..2 arrays with some element plus some horizontally, vertically, diagonally or antidiagonally adjacent neighbor totalling two exactly once. %C A268767 Diagonal of A268774. %H A268767 R. H. Hardin, <a href="/A268767/b268767.txt">Table of n, a(n) for n = 1..17</a> %e A268767 Some solutions for n=4 %e A268767 ..0..1..0..0. .1..2..2..2. .2..2..2..2. .0..1..0..0. .1..0..0..0 %e A268767 ..0..0..1..0. .1..2..2..2. .2..2..2..2. .1..0..0..0. .0..0..1..0 %e A268767 ..0..0..0..0. .2..2..2..2. .2..2..2..1. .0..0..0..0. .1..0..0..0 %e A268767 ..0..1..0..0. .2..1..2..2. .2..2..2..1. .1..0..1..0. .1..0..0..1 %Y A268767 Cf. A268774. %K A268767 nonn %O A268767 1,2 %A A268767 _R. H. Hardin_, Feb 13 2016