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%I #11 Jun 17 2018 07:25:50
%S 81,399,1620,6462,26481,110769,469617,2009553,8655441,37451697,
%T 162572721,707284113,3081856785,13442980209,58681197681,256284824145,
%U 1119691708881,4893034223409,21386003380017,93482466850833,408662174944401
%N Number of (n+1) X 2 0..2 arrays with the number of clockwise edge increases in 2 X 2 subblocks nondecreasing, and counterclockwise edge increases nonincreasing, rightwards and downwards.
%C Column 1 of A206542.
%H R. H. Hardin, <a href="/A206535/b206535.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 7*a(n-1) - 9*a(n-2) - 15*a(n-3) + 18*a(n-4) for n>8.
%F Empirical g.f.: 3*x*(27 - 56*x - 148*x^2 - 24*x^3 + 118*x^4 + 226*x^5 + 111*x^6 + 18*x^7) / ((1 - x)*(1 - 3*x)*(1 - 3*x - 6*x^2)). - _Colin Barker_, Jun 17 2018
%e Some solutions for n=4:
%e ..1..2....1..1....0..0....0..2....2..2....2..0....2..0....0..0....1..1....2..1
%e ..1..2....0..0....1..1....1..1....2..0....2..2....2..2....0..2....1..1....0..2
%e ..1..1....2..0....1..0....1..2....0..0....2..0....1..2....0..2....1..1....1..0
%e ..2..1....0..0....0..0....0..0....1..0....2..2....2..2....2..2....1..1....2..1
%e ..1..1....0..1....2..2....2..1....0..0....0..2....2..0....1..0....1..1....1..0
%Y Cf. A206542.
%K nonn
%O 1,1
%A _R. H. Hardin_, Feb 09 2012
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