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 A269220 #4 Feb 20 2016 11:34:29 %S A269220 0,7375872,2039727744,599456856000,163535201141376,43468685827935816, %T A269220 11273191243423937904,2872961996154823592256,722010748558146090563664, %U A269220 179436639887553691981747008,44187481124719769649267286128 %N A269220 Number of 7Xn 0..3 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling three exactly once. %C A269220 Row 7 of A269214. %H A269220 R. H. Hardin, <a href="/A269220/b269220.txt">Table of n, a(n) for n = 1..210</a> %e A269220 Some solutions for n=2 %e A269220 ..0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0 %e A269220 ..0..2. .0..0. .0..0. .0..0. .0..0. .0..2. .0..0. .0..0. .0..2. .0..0 %e A269220 ..2..0. .0..1. .1..0. .1..0. .0..0. .0..2. .1..1. .1..1. .0..0. .1..3 %e A269220 ..2..3. .3..3. .1..1. .2..3. .2..2. .2..2. .2..3. .0..1. .0..0. .3..1 %e A269220 ..1..1. .2..2. .1..3. .0..2. .3..3. .3..2. .2..2. .3..2. .1..3. .3..1 %e A269220 ..3..1. .2..3. .3..2. .3..2. .2..1. .0..3. .2..0. .1..3. .1..1. .3..2 %e A269220 ..3..2. .3..3. .3..2. .3..3. .0..0. .2..2. .1..3. .1..3. .0..0. .0..1 %Y A269220 Cf. A269214. %K A269220 nonn %O A269220 1,2 %A A269220 _R. H. Hardin_, Feb 20 2016