cp's OEIS Frontend

A221404 Number of nX3 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor, with every occupancy equal to zero or two.

%I A221404 #9 Jul 23 2025 01:52:54
%S A221404 0,16,0,436,0,12668,0,368268,0,10705360,0,311197280,0,9046269888,0,
%T A221404 262968117056,0,7644280337936,0,222213327464336,0,6459569820912704,0,
%U A221404 187774705858714240,0,5458465675503960896,0,158673381440822516672,0
%N A221404 Number of nX3 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor, with every occupancy equal to zero or two.
%C A221404 Column 3 of A221408
%H A221404 R. H. Hardin, <a href="/A221404/b221404.txt">Table of n, a(n) for n = 1..210</a>
%F A221404 Empirical: a(n) = 36*a(n-2) -200*a(n-4) -40*a(n-6) -84*a(n-8) +80*a(n-10) -20*a(n-12) +80*a(n-14)
%e A221404 Some solutions for n=4
%e A221404 ..0..2..0....2..0..2....2..0..2....0..2..0....0..2..0....2..0..0....0..2..2
%e A221404 ..2..0..0....2..0..0....0..0..2....0..0..2....0..2..0....0..2..2....0..0..0
%e A221404 ..2..2..2....0..0..2....0..0..2....2..2..2....2..0..2....0..0..0....2..0..2
%e A221404 ..0..2..0....2..2..0....2..0..2....0..0..2....2..0..2....2..2..2....2..2..0
%K A221404 nonn
%O A221404 1,2
%A A221404 _R. H. Hardin_ Jan 15 2013