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 A233023 #6 Jul 23 2025 07:47:29 %S A233023 81,2337,92067,3685017,149128385,6050598339,245698677999, %T A233023 9979662714381,405380056659145,16467175046293207,668927350000203943, %U A233023 27173135930635192613,1103826618460521163805,44839633474092471048067 %N A233023 Number of nX5 0..3 arrays with no element x(i,j) adjacent to value 3-x(i,j) horizontally, vertically, diagonally or antidiagonally, and top left element zero. %C A233023 Column 5 of A233026 %H A233023 R. H. Hardin, <a href="/A233023/b233023.txt">Table of n, a(n) for n = 1..210</a> %F A233023 Empirical: a(n) = 59*a(n-1) -780*a(n-2) +619*a(n-3) +32493*a(n-4) -90013*a(n-5) -408784*a(n-6) +1361086*a(n-7) +1750387*a(n-8) -6258928*a(n-9) -3161760*a(n-10) +10671769*a(n-11) +1911277*a(n-12) -7549998*a(n-13) +65894*a(n-14) +2257616*a(n-15) -323424*a(n-16) -231416*a(n-17) +54784*a(n-18) +784*a(n-19) -480*a(n-20) %e A233023 Some solutions for n=3 %e A233023 ..0..2..0..1..0....0..1..3..3..3....0..1..0..1..1....0..0..1..3..3 %e A233023 ..0..0..0..0..1....1..1..3..1..1....0..1..0..1..1....1..1..1..1..3 %e A233023 ..0..0..0..1..1....3..3..3..1..3....0..1..1..1..1....1..1..1..3..3 %K A233023 nonn %O A233023 1,1 %A A233023 _R. H. Hardin_, Dec 03 2013