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 A241440 #5 Jun 02 2025 10:09:25 %S A241440 15,6,381,5304,37148,377314,4122537,29425635,269064197,2138370398, %T A241440 17341166885 %N A241440 Number of 6Xn 0..3 arrays with no element equal to one plus the sum of elements to its left or one plus the sum of the elements above it or zero plus the sum of the elements diagonally to its northwest or one plus the sum of the elements antidiagonally to its northeast, modulo 4. %C A241440 Row 6 of A241435 %e A241440 Some solutions for n=3 %e A241440 ..3..3..2....3..3..2....3..2..3....3..3..2....3..3..2....2..2..3....3..2..3 %e A241440 ..2..2..2....3..2..0....2..1..3....2..2..0....2..2..2....2..1..3....2..2..3 %e A241440 ..3..1..2....2..0..0....3..3..2....3..3..2....3..1..0....3..3..2....3..3..2 %e A241440 ..2..2..2....2..0..2....2..0..2....3..2..3....2..0..2....2..2..3....2..2..2 %e A241440 ..2..0..0....2..0..0....2..1..2....2..2..3....2..0..2....3..3..2....2..1..2 %e A241440 ..2..0..0....2..0..0....3..1..2....3..3..2....2..0..0....2..2..3....2..1..2 %K A241440 nonn %O A241440 1,1 %A A241440 _R. H. Hardin_, Apr 22 2014