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Number of nX3 0..2 arrays with no element unequal to a strict majority of its horizontal, vertical and antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.
1

%I #4 Dec 29 2016 04:01:29

%S 0,26,158,886,4382,20593,93326,410789,1768582,7492763,31338310,

%T 129696524,531993558,2165446751,8755471090,35192210828,140712962436,

%U 559989349075,2219142915606,8760369870437,34461931251266,135134230809249

%N Number of nX3 0..2 arrays with no element unequal to a strict majority of its horizontal, vertical and antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.

%C Column 3 of A280217.

%H R. H. Hardin, <a href="/A280213/b280213.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 9*a(n-1) -12*a(n-2) -96*a(n-3) +273*a(n-4) +165*a(n-5) -1237*a(n-6) +1107*a(n-7) +1053*a(n-8) -3215*a(n-9) +2415*a(n-10) +219*a(n-11) -622*a(n-12) -600*a(n-13) +1371*a(n-14) -349*a(n-15) -468*a(n-16) -108*a(n-17) +80*a(n-18) -240*a(n-19) -192*a(n-20) -64*a(n-21) for n>28

%e Some solutions for n=4

%e ..0..1..1. .0..0..1. .0..1..2. .0..0..0. .0..1..2. .0..1..1. .0..1..2

%e ..0..1..0. .0..0..1. .0..2..2. .0..0..1. .1..2..2. .1..1..2. .1..1..2

%e ..0..0..0. .0..1..1. .0..0..2. .0..2..0. .1..2..2. .2..2..1. .1..1..2

%e ..0..0..1. .1..1..2. .0..0..2. .0..0..0. .1..1..1. .2..1..1. .1..1..2

%Y Cf. A280217.

%K nonn

%O 1,2

%A _R. H. Hardin_, Dec 29 2016