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 A229843 #6 Jun 02 2025 08:38:56 %S A229843 9,423,13401,453837,15269193,514371027,17324310663,583513743897, %T A229843 19653679602141,661968066724119,22296164158938861,750971189107675233, %U A229843 25293934916476773699,851940997449956765547,28694762814404871782187 %N A229843 Number of nX4 0..2 arrays x(i,j) with each element horizontally or vertically next to at least one element with value 2-x(i,j). %C A229843 Column 4 of A229847 %H A229843 R. H. Hardin, <a href="/A229843/b229843.txt">Table of n, a(n) for n = 1..210</a> %F A229843 Empirical: a(n) = 28*a(n-1) +223*a(n-2) -810*a(n-3) -8714*a(n-4) -856*a(n-5) +147241*a(n-6) +236084*a(n-7) -1172242*a(n-8) -3528345*a(n-9) +678458*a(n-10) +16652175*a(n-11) +101500683*a(n-12) -128462366*a(n-13) -411090364*a(n-14) +905075331*a(n-15) -2603919959*a(n-16) +5803974821*a(n-17) -7111289023*a(n-18) +9684239810*a(n-19) -13438664953*a(n-20) +15373544589*a(n-21) -17181774335*a(n-22) +14938323369*a(n-23) -15592749244*a(n-24) +3820796842*a(n-25) +4237587780*a(n-26) -3292600679*a(n-27) +15021433542*a(n-28) -4461452087*a(n-29) -11101458512*a(n-30) +37414533509*a(n-31) -67227775904*a(n-32) +83523691644*a(n-33) -116673702936*a(n-34) +124723830770*a(n-35) -123437354031*a(n-36) +134526294777*a(n-37) -110378277541*a(n-38) +89122202017*a(n-39) -80590207954*a(n-40) +64320664361*a(n-41) -49928847307*a(n-42) +30705120692*a(n-43) -25484291913*a(n-44) +22612424455*a(n-45) -10724796799*a(n-46) +6043765216*a(n-47) -4421780238*a(n-48) +2556973448*a(n-49) -1102876952*a(n-50) +274132088*a(n-51) -116104448*a(n-52) -5874816*a(n-53) %e A229843 Some solutions for n=3 %e A229843 ..2..0..2..0....2..0..2..1....2..1..1..0....2..0..2..0....1..1..1..1 %e A229843 ..2..2..2..2....1..0..0..1....0..0..2..2....0..0..2..1....2..0..2..0 %e A229843 ..0..0..0..2....1..2..2..0....2..2..0..2....1..1..0..1....2..0..0..2 %K A229843 nonn %O A229843 1,1 %A A229843 _R. H. Hardin_, Oct 01 2013