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 A268782 #7 Apr 19 2020 23:43:25 %S A268782 0,5,72,1714,67100,4725018,611932378,148013550916,67580406047498, %T A268782 58605374440440754,97015414668307967168,307604236621005318739500, %U A268782 1873151902121241161650454526,21951627197224261891003815976598 %N A268782 Number of n X n binary arrays with some element plus some horizontally, vertically or antidiagonally adjacent neighbor totalling two exactly once. %C A268782 Diagonal of A268789. %H A268782 R. H. Hardin, <a href="/A268782/b268782.txt">Table of n, a(n) for n = 1..26</a> %e A268782 Some solutions for n=4 %e A268782 ..0..1..0..0. .0..1..0..0. .0..0..0..1. .0..0..1..0. .0..0..1..0 %e A268782 ..0..0..0..1. .0..1..0..0. .1..0..0..0. .1..0..1..0. .0..0..0..1 %e A268782 ..1..1..0..0. .0..0..1..0. .0..0..1..0. .0..0..0..0. .0..1..0..0 %e A268782 ..0..0..0..0. .1..0..0..1. .1..0..1..0. .0..1..0..0. .0..0..1..1 %Y A268782 Cf. A268789. %K A268782 nonn %O A268782 1,2 %A A268782 _R. H. Hardin_, Feb 13 2016