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 #4 Jan 22 2013 07:15:28
%S 1,987,63676,7033429,659020617,64509677154,6233675847228,
%T 604346923784252,58538232535028520,5671250113728678882,
%U 549411330594167686392,53225495837252796349285,5156336905625087231654148
%N Number of 4Xn arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without consecutive moves in the same direction
%C Row 4 of A221693
%H R. H. Hardin, <a href="/A221696/b221696.txt">Table of n, a(n) for n = 1..18</a>
%e Some solutions for n=3
%e ..2..0..0....2..0..1....0..1..1....1..0..0....0..4..1....1..0..0....0..3..2
%e ..0..3..1....1..1..0....2..3..0....1..4..0....0..0..1....2..2..1....0..0..1
%e ..1..0..1....2..0..0....0..0..0....2..0..2....2..1..0....0..2..0....1..2..1
%e ..1..3..0....1..3..1....2..1..2....0..1..1....0..3..0....1..3..0....1..0..1
%K nonn
%O 1,2
%A _R. H. Hardin_ Jan 22 2013