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 A240152 #5 Jun 02 2025 09:40:37 %S A240152 15,57,450,5701,88214,1608415,30542203,584983851,11643589675, %T A240152 228028231216 %N A240152 Number of nX6 0..3 arrays with no element equal to one plus the sum of elements to its left or one plus the sum of elements above it or one plus the sum of the elements diagonally to its northwest or zero plus the sum of the elements antidiagonally to its northeast, modulo 4. %C A240152 Column 6 of A240153 %e A240152 Some solutions for n=3 %e A240152 ..2..2..3..3..2..2....3..3..2..3..2..3....2..2..3..2..3..2....2..2..3..2..3..3 %e A240152 ..0..2..1..3..1..2....2..1..2..1..2..2....0..2..1..2..1..1....0..2..1..1..2..1 %e A240152 ..0..2..2..2..1..3....0..0..0..3..3..1....2..2..2..2..3..2....2..2..3..2..3..2 %K A240152 nonn %O A240152 1,1 %A A240152 _R. H. Hardin_, Apr 02 2014