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 A240402 #6 Jun 02 2025 09:54:46 %S A240402 3,14,77,235,1381,5566,21413,114951,447479,1942846,9296148,37136986, %T A240402 169442132,756650294,3157572233,14387587626,62384424058,269023025478, %U A240402 1206596042127,5204663585354,22811833314490,100879086151468 %N A240402 Number of nX3 0..3 arrays with no element equal to one plus the sum of elements to its left or three plus the sum of elements above it or zero plus the sum of the elements diagonally to its northwest, modulo 4. %C A240402 Column 3 of A240406 %H A240402 R. H. Hardin, <a href="/A240402/b240402.txt">Table of n, a(n) for n = 1..210</a> %e A240402 Some solutions for n=4 %e A240402 ..2..1..1....2..1..1....2..2..2....2..1..1....2..2..2....2..1..1....2..2..2 %e A240402 ..3..1..2....3..1..3....3..3..0....3..1..2....3..3..0....3..1..2....3..3..0 %e A240402 ..2..0..1....2..0..0....3..1..3....3..2..0....2..2..0....2..0..0....3..1..3 %e A240402 ..3..3..0....3..3..0....2..2..2....2..0..0....3..3..0....3..3..1....2..0..2 %K A240402 nonn %O A240402 1,1 %A A240402 _R. H. Hardin_, Apr 04 2014