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%I #9 Jul 15 2018 06:53:34
%S 112,1578,22212,312704,4402192,61973516,872455004,12282307884,
%T 172908727756,2434186513236,34268160178956,482422688537636,
%U 6791483674595260,95609621185469444,1345979774260696316
%N Half the number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having at most one duplicate clockwise edge difference.
%C Column 1 of A210300.
%H R. H. Hardin, <a href="/A210293/b210293.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 11*a(n-1) + 42*a(n-2) + 20*a(n-3) - 18*a(n-4).
%F Empirical g.f.: 2*x*(56 + 173*x + 75*x^2 - 72*x^3) / (1 - 11*x - 42*x^2 - 20*x^3 + 18*x^4). - _Colin Barker_, Jul 15 2018
%e Some solutions for n=4:
%e ..2..0....3..1....3..2....1..3....1..1....1..0....2..3....1..0....1..3....2..1
%e ..3..0....1..0....3..0....1..3....2..2....2..0....0..1....0..0....2..2....1..1
%e ..2..0....2..2....1..1....3..2....1..0....1..2....2..0....0..3....0..2....3..3
%e ..3..1....1..1....1..2....1..3....0..3....1..3....0..1....1..3....2..1....0..1
%e ..1..2....0..3....2..2....0..1....0..0....0..0....3..0....1..0....1..1....0..0
%Y Cf. A210300.
%K nonn
%O 1,1
%A _R. H. Hardin_, Mar 19 2012