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%I #9 Jul 15 2018 12:03:02
%S 73,597,4881,39909,326313,2668077,21815361,178371909,1458446553,
%T 11924895357,97503147441,797228275509,6518486222793,53297987467437,
%U 435787600217121,3563189559812709,29134192512207033,238213869649684317
%N Number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock having one, two or three distinct clockwise edge differences.
%C Column 1 of A210390.
%H R. H. Hardin, <a href="/A210383/b210383.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 9*a(n-1) - 6*a(n-2) - 6*a(n-3).
%F Empirical g.f.: x*(73 - 60*x - 54*x^2) / (1 - 9*x + 6*x^2 + 6*x^3). - _Colin Barker_, Jul 15 2018
%e Some solutions for n=4:
%e ..0..0....2..1....2..1....0..2....2..1....2..0....2..1....1..2....1..2....0..2
%e ..2..1....0..0....1..1....2..0....0..0....1..0....0..0....0..1....0..2....0..1
%e ..2..0....2..0....0..1....0..2....1..1....0..0....1..1....2..1....0..2....2..1
%e ..1..0....0..2....2..2....0..1....1..2....1..0....1..0....2..0....2..2....1..0
%e ..0..0....1..1....1..2....1..2....1..1....2..1....2..1....0..2....0..2....0..0
%Y Cf. A210390.
%K nonn
%O 1,1
%A _R. H. Hardin_, Mar 20 2012