%I #10 Aug 04 2018 06:40:46
%S 3,33,352,3721,39254,413908,4363921,46008619,485064009,5113971944,
%T 53915979657,568429529006,5992882377940,63182219138721,
%U 666122336505939,7022845559348401,74040993741513520,780605056433123273
%N Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal, vertical or antidiagonal neighbor.
%C Column 2 of A221165.
%H R. H. Hardin, <a href="/A221162/b221162.txt">Table of n, a(n) for n = 1..23</a>
%F Empirical: a(n) = 13*a(n-1) - 26*a(n-2) + a(n-3).
%F Empirical g.f.: x*(3 - 6*x + x^2) / (1 - 13*x + 26*x^2 - x^3). - _Colin Barker_, Aug 04 2018
%e Some solutions for n=3:
%e ..0..0....3..1....1..0....0..0....0..0....2..0....1..0....0..2....3..1....0..3
%e ..3..0....0..1....2..2....2..1....3..1....2..1....0..3....0..0....0..0....1..1
%e ..2..1....0..1....1..0....3..0....1..1....1..0....2..0....4..0....2..0....1..0
%Y Cf. A221165.
%K nonn
%O 1,1
%A _R. H. Hardin_, Jan 03 2013