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 A230646 #7 Jun 02 2025 08:43:31 %S A230646 0,3,3,123,1635,337977,31908483,40860127671,24818871787539, %T A230646 201844710508818147,781457119775191627041,40464088148356899296269059, %U A230646 997750456877626717987299707229 %N A230646 Number of n X n 0..2 white square subarrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value 2-x(i,j). %C A230646 Diagonal of A230652 %e A230646 Some solutions for n=5 %e A230646 ..0..x..0..x..2....1..x..2..x..2....0..x..0..x..1....2..x..2..x..0 %e A230646 ..x..2..x..0..x....x..1..x..0..x....x..2..x..1..x....x..0..x..2..x %e A230646 ..0..x..2..x..2....2..x..2..x..1....2..x..0..x..1....2..x..1..x..0 %e A230646 ..x..1..x..2..x....x..0..x..1..x....x..0..x..1..x....x..1..x..0..x %e A230646 ..1..x..0..x..0....2..x..1..x..1....2..x..2..x..1....1..x..1..x..2 %K A230646 nonn %O A230646 1,2 %A A230646 _R. H. Hardin_, Oct 27 2013