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 A269179 #6 Apr 20 2020 19:50:22 %S A269179 0,48,5888,2097552,2563440512,11426543880704,192247800095048896, %T A269179 12445275374147703433760,3138050414883209885285902752, %U A269179 3107560086436286975829696986907248 %N A269179 Number of n X n 0..3 arrays with some element plus some horizontally, diagonally, antidiagonally or vertically adjacent neighbor totalling three exactly once. %C A269179 Diagonal of A269186. %e A269179 Some solutions for n=3 %e A269179 ..0..1..1. .0..2..3. .1..1..1. .3..2..3. .0..2..2. .1..1..0. .3..1..3 %e A269179 ..1..0..0. .2..2..2. .3..1..1. .3..2..0. .0..2..3. .0..0..2. .3..2..3 %e A269179 ..0..1..2. .2..0..3. .0..1..1. .2..2..0. .3..2..3. .0..0..0. .3..2..3 %Y A269179 Cf. A269186. %K A269179 nonn %O A269179 1,2 %A A269179 _R. H. Hardin_, Feb 20 2016