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Number of nX2 0..2 arrays with every element neighboring horizontally or vertically both a 0 and a 1
2

%I #9 Mar 31 2012 12:36:57

%S 0,4,4,16,64,196,676,2304,7744,26244,88804,300304,1016064,3437316,

%T 11628100,39337984,133079296,450203524,1523028676,5152368400,

%U 17430336576,58966408900,199481929956,674842534144,2282975946304,7723252297476

%N Number of nX2 0..2 arrays with every element neighboring horizontally or vertically both a 0 and a 1

%C Column 2 of A203542

%C (A135491(n-2))^2 for n>=3

%H R. H. Hardin, <a href="/A203536/b203536.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 2*a(n-1) +3*a(n-2) +6*a(n-3) -a(n-4) -a(n-6)

%e Some solutions for n=5

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

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

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_ Jan 02 2012