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 A239401 #6 Jun 02 2025 09:27:21 %S A239401 16,478,13977,394509,11334364,326882784,9402398952,270516990628, %T A239401 7789048968124,224284362847360,6457977012007180,185957590016422087, %U A239401 5354807669541831222,154196812648221842975,4440254588265618959278 %N A239401 Number of nX4 0..3 arrays with no element equal to one plus the sum of elements to its left or two plus the sum of elements above it, modulo 4. %C A239401 Column 4 of A239405 %H A239401 R. H. Hardin, <a href="/A239401/b239401.txt">Table of n, a(n) for n = 1..210</a> %e A239401 Some solutions for n=3 %e A239401 ..3..3..1..1....3..1..3..3....3..1..3..3....0..0..3..1....3..1..0..0 %e A239401 ..2..0..0..2....0..0..3..3....2..1..2..0....3..1..2..1....0..0..0..0 %e A239401 ..2..0..2..2....2..1..1..3....0..3..1..0....2..2..2..2....2..2..3..1 %K A239401 nonn %O A239401 1,1 %A A239401 _R. H. Hardin_, Mar 17 2014