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 A230681 #5 Jun 02 2025 08:45:46 %S A230681 0,63291,53519163,42681522741,47444197636239,51564141085334199, %T A230681 55314799986833459367,59453762981075686349985, %U A230681 63928300225239002685024369 %N A230681 Number of 7Xn 0..2 arrays x(i,j) with each element horizontally, diagonally or antidiagonally next to at least one element with value 2-x(i,j). %C A230681 Row 7 of A230675 %e A230681 Some solutions for n=3 %e A230681 ..0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0 %e A230681 ..0..2..2....0..2..2....0..2..2....0..2..2....0..2..2....0..2..2....0..2..2 %e A230681 ..0..1..0....0..1..1....0..0..0....0..1..0....0..0..0....0..0..0....0..0..1 %e A230681 ..1..2..0....0..2..2....1..2..0....1..2..1....1..0..2....0..2..0....1..1..1 %e A230681 ..2..0..2....0..0..2....0..1..1....2..1..1....2..1..0....0..1..1....0..2..1 %e A230681 ..1..0..2....0..2..0....1..2..0....0..0..0....2..2..2....1..2..1....2..2..2 %e A230681 ..1..1..1....1..1..1....2..0..2....0..2..2....0..0..0....2..0..2....0..0..0 %K A230681 nonn %O A230681 1,2 %A A230681 _R. H. Hardin_, Oct 27 2013