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 A241104 #6 Jul 23 2025 11:09:09 %S A241104 4,36,294,2436,19814,162776,1333934,10937316,89651534,734979136, %T A241104 6025149574,49393306556,404916355574,3319433387656,27212098788254, %U A241104 223079838087956,1828767624421854,14991902921730896,122900877847563254 %N A241104 Number of nX4 0..2 arrays with no element equal to one or three horizontal or vertical neighbors, with new values 0..2 introduced in row major order. %C A241104 Column 4 of A241108 %H A241104 R. H. Hardin, <a href="/A241104/b241104.txt">Table of n, a(n) for n = 1..210</a> %F A241104 Empirical: a(n) = 6*a(n-1) +21*a(n-2) -12*a(n-3) +8*a(n-4) -688*a(n-5) -1648*a(n-6) -768*a(n-7) -2304*a(n-8) +8192*a(n-9) +16384*a(n-10) %e A241104 Some solutions for n=4 %e A241104 ..0..1..2..0....0..1..1..2....0..1..0..2....0..1..2..1....0..0..1..2 %e A241104 ..1..2..0..1....2..1..1..0....1..0..1..0....1..0..1..0....0..0..2..1 %e A241104 ..2..0..1..0....0..2..0..1....0..2..2..1....2..1..2..1....1..2..1..2 %e A241104 ..0..1..0..2....1..0..1..0....1..2..2..0....1..0..1..0....0..1..2..1 %K A241104 nonn %O A241104 1,1 %A A241104 _R. H. Hardin_, Apr 16 2014