Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #7 Dec 24 2018 16:21:32
%S 21,65,192,581,1733,5216,15613,46897,140568,421901,1265269,3796472,
%T 11387877,34165857,102492080,307483605,922431077,2767317200,
%U 8301880013,24905716177,74716886152,224150891421,672451700885,2017355772136
%N Number of (n+1) X (2+1) 0..1 arrays with each 2 X 2 subblock having clockwise pattern 0000 0011 or 0111.
%H R. H. Hardin, <a href="/A259244/b259244.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 3*a(n-1) + 4*a(n-2) - 11*a(n-3) - 3*a(n-4).
%F Empirical g.f.: x*(21 + 2*x - 87*x^2 - 24*x^3) / ((1 - 3*x)*(1 - 4*x^2 - x^3)). - _Colin Barker_, Dec 24 2018
%e Some solutions for n=4:
%e ..0..1..0....1..0..0....1..0..0....1..1..1....0..1..0....0..0..1....0..1..1
%e ..0..1..0....1..0..0....1..1..1....0..0..1....1..1..1....1..1..1....0..1..0
%e ..1..1..1....1..1..1....1..0..0....1..1..1....1..0..0....0..0..1....1..1..0
%e ..0..0..0....1..0..0....1..1..1....0..1..0....1..1..1....1..1..1....0..1..1
%e ..1..1..1....1..1..1....1..0..0....0..1..0....1..0..0....0..0..0....1..1..0
%Y Column 2 of A259250.
%K nonn
%O 1,1
%A _R. H. Hardin_, Jun 22 2015