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 A239409 #6 Jun 02 2025 09:28:09 %S A239409 66,3805,205969,11334364,614216271,33522573911,1820591502437, %T A239409 99155297311831,5390539057008613,293381673332485198, %U A239409 15956203146991156417,868193383242995642964,47226335011968154541246,2569370658950018916786902 %N A239409 Number of 5Xn 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 A239409 Row 5 of A239405 %H A239409 R. H. Hardin, <a href="/A239409/b239409.txt">Table of n, a(n) for n = 1..210</a> %e A239409 Some solutions for n=3 %e A239409 ..0..0..3....0..3..1....0..0..3....3..1..0....0..3..1....3..3..0....0..0..0 %e A239409 ..3..1..0....3..3..2....0..3..2....2..2..0....3..3..2....0..2..0....0..0..3 %e A239409 ..2..0..0....0..3..2....0..3..1....2..0..0....3..1..3....2..1..3....0..0..0 %e A239409 ..0..0..2....0..2..2....3..1..3....0..2..0....3..2..3....0..2..2....3..3..2 %e A239409 ..0..2..2....2..0..0....2..0..0....0..0..3....2..1..1....0..0..0....3..3..1 %K A239409 nonn %O A239409 1,1 %A A239409 _R. H. Hardin_, Mar 17 2014