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A185513 Number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock singular. 1

%I

%S 31,143,593,2553,10847,46303,197329,841449,3587359,15295151,65211089,

%T 278030937,1185395807,5053987327,21547889233,91870352457,391693178911,

%U 1670000659151,7120119353681,30356933960889,129428088631391

%N Number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock singular.

%C Column 1 of A185521.

%H R. H. Hardin, <a href="/A185513/b185513.txt">Table of n, a(n) for n = 1..200</a>

%F Empirical: a(n) = 4*a(n-1) + 3*a(n-2) - 8*a(n-3).

%F Empirical g.f.: x*(31 + 19*x - 72*x^2) / (1 - 4*x - 3*x^2 + 8*x^3). - _Colin Barker_, Apr 16 2018

%e Some solutions for 3 X 2:

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

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

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

%Y Cf. A185521.

%K nonn

%O 1,1

%A _R. H. Hardin_, Jan 29 2011

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Last modified May 20 10:33 EDT 2022. Contains 353871 sequences. (Running on oeis4.)