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 A269195 #6 Apr 20 2020 19:51:23 %S A269195 4,180,25572,15289548,34838403756,320994710282892, %T A269195 12093315071771856492,1887658657444603460395332, %U A269195 1230222115345954315761363474780,3366670969596963372379333414861881876 %N A269195 Number of n X n 0..3 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling three no more than once. %C A269195 Diagonal of A269201. %e A269195 Some solutions for n=3 %e A269195 ..0..2..0. .0..1..0. .3..1..3. .0..0..1. .1..0..0. .3..1..2. .0..0..0 %e A269195 ..0..1..3. .1..1..1. .0..3..3. .0..0..1. .1..0..1. .3..2..0. .2..0..0 %e A269195 ..0..1..3. .3..1..3. .3..1..1. .0..1..0. .3..3..1. .2..2..0. .2..0..1 %Y A269195 Cf. A269201. %K A269195 nonn %O A269195 1,1 %A A269195 _R. H. Hardin_, Feb 20 2016