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 A239823 #6 Jun 02 2025 09:33:22 %S A239823 57,2981,204779,13597573,884977259,58232200212,3842974545029, %T A239823 253291756984373,16698512969146104,1101377884320804108, %U A239823 72647284903645567684,4791845462621985366247,316083646998469552591720 %N A239823 Number of 5Xn 0..3 arrays with no element equal to zero plus the sum of elements to its left or one plus the sum of the elements above it, modulo 4. %C A239823 Row 5 of A239819 %H A239823 R. H. Hardin, <a href="/A239823/b239823.txt">Table of n, a(n) for n = 1..210</a> %e A239823 Some solutions for n=2 %e A239823 ..3..2....3..0....2..3....3..2....2..0....2..0....3..0....2..3....3..2....2..0 %e A239823 ..2..1....3..2....2..1....3..0....1..3....1..0....1..0....1..3....1..0....1..2 %e A239823 ..3..1....1..2....3..0....2..1....2..1....1..0....2..3....2..1....3..1....3..1 %e A239823 ..3..0....1..2....3..0....2..1....3..2....3..0....1..2....3..1....1..2....1..3 %e A239823 ..2..0....3..0....2..3....1..0....2..1....2..0....2..0....3..2....2..3....2..1 %K A239823 nonn %O A239823 1,1 %A A239823 _R. H. Hardin_, Mar 27 2014