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A221726 Number of nX3 arrays of occupancy after each element stays put or moves to some horizontal, diagonal or antidiagonal neighbor, with every occupancy equal to zero or two.

%I A221726 #9 Jul 23 2025 02:08:06
%S A221726 0,16,0,464,0,13948,0,420736,0,12695288,0,383074904,0,11559126552,0,
%T A221726 348791805904,0,10524646286488,0,317576778411352,0,9582745781519416,0,
%U A221726 289155325092787296,0,8725140362031620984,0,263277441988312544616,0
%N A221726 Number of nX3 arrays of occupancy after each element stays put or moves to some horizontal, diagonal or antidiagonal neighbor, with every occupancy equal to zero or two.
%C A221726 Column 3 of A221728
%H A221726 R. H. Hardin, <a href="/A221726/b221726.txt">Table of n, a(n) for n = 1..210</a>
%F A221726 Empirical: a(n) = 44*a(n-2) -462*a(n-4) +1400*a(n-6) -1417*a(n-8) -448*a(n-10) -280*a(n-12) +100*a(n-14)
%e A221726 Some solutions for n=4
%e A221726 ..0..0..2....0..2..2....0..2..0....2..2..0....2..2..0....2..0..0....0..2..2
%e A221726 ..2..2..0....2..0..0....2..2..2....2..0..0....0..2..2....0..2..2....0..2..0
%e A221726 ..0..2..2....0..2..0....0..2..0....0..2..0....0..2..0....2..0..0....2..0..0
%e A221726 ..2..0..0....2..0..2....0..0..2....0..2..2....0..0..2....2..2..0....2..2..0
%K A221726 nonn
%O A221726 1,2
%A A221726 _R. H. Hardin_ Jan 22 2013