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%I #9 Jun 13 2018 05:47:31
%S 24,78,228,722,2136,6688,19976,62048,186560,576288,1740672,5356544,
%T 16230528,49815040,151270400,463442432,1409423360,4312621056,
%U 13129156608,40138661888,122283737088,373625921536,1138824544256,3478142320640
%N Number of (n+1) X 2 0..2 arrays with the number of clockwise edge increases in every 2 X 2 subblock equal to one, and every 2 X 2 determinant nonzero.
%C Column 1 of A206010.
%H R. H. Hardin, <a href="/A206003/b206003.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 8*a(n-2) + 4*a(n-3) for n>4.
%F Empirical g.f.: 2*x*(12 + 39*x + 18*x^2 + x^3) / (1 - 8*x^2 - 4*x^3). - _Colin Barker_, Jun 13 2018
%e Some solutions for n=4:
%e ..2..1....1..1....2..1....1..0....2..0....2..1....2..1....1..0....0..1....2..0
%e ..2..2....0..1....2..2....2..2....2..2....0..1....1..1....1..2....1..1....2..2
%e ..2..0....1..1....1..2....1..2....0..2....1..1....1..2....2..2....1..2....2..0
%e ..2..2....0..1....1..1....1..1....2..2....2..1....1..1....0..1....1..1....2..2
%e ..1..2....1..1....1..0....0..1....1..2....1..1....1..2....1..1....0..1....0..1
%Y Cf. A206010.
%K nonn
%O 1,1
%A _R. H. Hardin_, Feb 02 2012
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