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%I #8 Jul 12 2018 15:31:43
%S 64,576,5074,44948,397734,3520628,31161462,275819644,2441352670,
%T 21609092620,191268034094,1692966274828,14984912401894,
%U 132635602320228,1173994381706142,10391348815984084,91976700981777710,814111206705377460
%N Half the number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having exactly one duplicate clockwise edge difference.
%C Column 1 of A209787.
%H R. H. Hardin, <a href="/A209780/b209780.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 7*a(n-1) + 22*a(n-2) - 39*a(n-3) - 95*a(n-4) + 30*a(n-6).
%F Empirical g.f.: 2*x*(32 + 64*x - 183*x^2 - 373*x^3 + 7*x^4 + 120*x^5) / (1 - 7*x - 22*x^2 + 39*x^3 + 95*x^4 - 30*x^6). - _Colin Barker_, Jul 12 2018
%e Some solutions for n=4:
%e ..0..2....2..0....3..3....1..2....1..1....1..1....1..2....3..1....1..0....0..0
%e ..0..1....2..2....0..3....0..2....3..2....2..1....0..2....3..3....0..0....1..0
%e ..0..0....1..1....0..0....2..2....1..1....2..3....0..0....1..1....0..3....2..0
%e ..2..2....0..1....3..3....0..0....1..0....1..3....0..1....3..1....2..1....2..1
%e ..1..2....1..1....3..1....2..2....0..0....1..1....0..1....1..1....0..1....1..1
%Y Cf. A209787.
%K nonn
%O 1,1
%A _R. H. Hardin_, Mar 13 2012