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 A260834 #6 Jun 02 2025 12:11:21 %S A260834 48,82,188,364,644,1320,2584,4842,9412,18210,35192,68158,130812, %T A260834 253334,491376,945170,1825292,3533066,6818232,13167414,25439060, %U A260834 49131310,94931752,183337586,354061772,684091450,1321342040,2551947046,4929738068 %N A260834 Number of (n+2)X(1+2) 0..1 arrays with each 3X3 subblock having clockwise perimeter pattern 00000001 00000011 or 00010101. %C A260834 Column 1 of A260841 %H A260834 R. H. Hardin, <a href="/A260834/b260834.txt">Table of n, a(n) for n = 1..210</a> %F A260834 Empirical: a(n) = 4*a(n-3) +3*a(n-4) +4*a(n-5) +12*a(n-8) +12*a(n-9) -8*a(n-11) -12*a(n-12) -12*a(n-13) -8*a(n-14) for n>15 %e A260834 Some solutions for n=4 %e A260834 ..0..0..1....1..0..0....0..0..0....0..0..0....0..1..0....1..0..0....0..0..0 %e A260834 ..0..0..1....0..1..0....0..0..1....1..0..0....0..0..1....0..0..0....0..0..0 %e A260834 ..0..0..0....0..0..0....0..0..0....0..0..0....0..1..0....0..0..0....0..0..1 %e A260834 ..0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..1..0....0..0..0 %e A260834 ..0..0..1....0..1..0....1..1..0....1..0..0....0..0..0....0..0..1....1..0..1 %e A260834 ..0..0..1....1..0..0....1..0..0....0..0..0....0..1..0....0..1..0....0..1..0 %Y A260834 Cf. A260841 %K A260834 nonn %O A260834 1,1 %A A260834 _R. H. Hardin_, Aug 01 2015