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 A200664 #7 Jun 02 2025 07:19:15 %S A200664 5,15,45,135,406,1217,3650,10959,32941,99044,297812,895494,2692703, %T A200664 8096855,24346869,73209872,220138513,661945308,1990435887,5985139586, %U A200664 17997009753,54116091662,162724331983,489303778636,1471311543936 %N A200664 Number of 0..4 arrays x(0..n-1) of n elements with each no smaller than the sum of its three previous neighbors modulo 5. %C A200664 Column 4 of A200668 %H A200664 R. H. Hardin, <a href="/A200664/b200664.txt">Table of n, a(n) for n = 1..210</a> %e A200664 Some solutions for n=6 %e A200664 ..1....0....2....1....2....3....0....1....2....3....1....0....0....0....1....0 %e A200664 ..4....1....3....3....3....4....0....2....3....4....4....4....0....1....2....1 %e A200664 ..1....3....3....4....1....4....0....3....1....3....4....4....0....4....4....2 %e A200664 ..3....4....4....3....2....2....0....2....2....3....4....4....3....2....2....3 %e A200664 ..4....4....0....3....1....0....1....4....2....1....2....4....4....4....4....2 %e A200664 ..4....1....2....2....4....4....2....4....0....2....2....3....3....4....3....2 %K A200664 nonn %O A200664 1,1 %A A200664 _R. H. Hardin_ Nov 20 2011