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 A240514 #6 Jul 23 2025 11:02:01 %S A240514 3,6,10,28,73,196,515,1376,3686,9914,26681,71876,193749,522510, %T A240514 1409414,3802164,10257707,27675148,74669353,201466240,543583450, %U A240514 1466670482,3957312647,10677488468,28809678971,77733469590,209738364682 %N A240514 Number of nX3 0..1 arrays with no element equal to exactly two horizontal and vertical neighbors, with new values 0..1 introduced in row major order. %C A240514 Column 3 of A240519 %H A240514 R. H. Hardin, <a href="/A240514/b240514.txt">Table of n, a(n) for n = 1..210</a> %F A240514 Empirical: a(n) = 4*a(n-1) -3*a(n-2) -2*a(n-3) +2*a(n-4) +2*a(n-5) -7*a(n-6) -8*a(n-7) +15*a(n-8) +4*a(n-9) -8*a(n-10) -4*a(n-11) +15*a(n-12) +8*a(n-13) -7*a(n-14) -2*a(n-15) +2*a(n-16) +2*a(n-17) -3*a(n-18) -4*a(n-19) -a(n-20) %e A240514 Some solutions for n=4 %e A240514 ..0..1..0....0..1..0....0..1..0....0..1..0....0..1..0....0..1..1....0..1..0 %e A240514 ..1..0..0....1..0..1....0..0..1....1..1..1....0..0..1....1..0..0....1..0..0 %e A240514 ..0..1..0....0..1..0....0..1..0....0..0..0....0..1..0....0..1..1....1..1..0 %e A240514 ..1..0..1....1..0..1....1..1..1....1..0..1....1..0..1....1..0..0....1..0..1 %K A240514 nonn %O A240514 1,1 %A A240514 _R. H. Hardin_, Apr 06 2014