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 A269090 #6 Apr 19 2020 23:47:37 %S A269090 0,96,31296,37963968,211625837280,5826856525990272, %T A269090 819944297332124826720,600994567853371717147309536, %U A269090 2321584677123190401202986846749664,47631920426007575412576023256743509016160 %N A269090 Number of n X n 0..3 arrays with some element plus some horizontally or vertically adjacent neighbor totalling three exactly once. %C A269090 Diagonal of A269097. %H A269090 R. H. Hardin, <a href="/A269090/b269090.txt">Table of n, a(n) for n = 1..11</a> %e A269090 Some solutions for n=3 %e A269090 ..2..1..1. .1..3..2. .2..3..3. .2..3..3. .0..0..0. .2..0..1. .3..3..2 %e A269090 ..0..1..0. .3..3..3. .3..3..1. .0..1..1. .1..0..2. .3..2..2. .2..3..2 %e A269090 ..0..1..1. .1..2..2. .2..2..2. .1..0..3. .1..2..3. .3..3..3. .1..3..2 %Y A269090 Cf. A269097. %K A269090 nonn %O A269090 1,2 %A A269090 _R. H. Hardin_, Feb 19 2016