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 A239398 #7 May 19 2023 07:58:03 %S A239398 2,23,1337,394509,614216271,5072216819342,217822754771248124, %T A239398 49235710631611399112515,58260708510317695923927600575 %N A239398 Number of n X n 0..3 arrays with no element equal to one plus the sum of elements to its left or two plus the sum of the elements above it, modulo 4. %C A239398 Diagonal of A239405. %e A239398 Some solutions for n=3 %e A239398 ..0..3..3....0..3..1....3..1..0....0..0..0....3..1..0....0..0..0....3..3..1 %e A239398 ..3..3..2....0..2..0....2..2..3....0..0..0....0..2..1....3..1..3....3..3..2 %e A239398 ..3..1..2....0..0..0....2..2..2....3..3..1....0..0..0....3..1..2....2..2..2 %Y A239398 Cf. A239405. %K A239398 nonn %O A239398 1,1 %A A239398 _R. H. Hardin_, Mar 17 2014