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%I #7 Dec 13 2015 18:47:07
%S 81,2691,166605,25229685,10351091007,11143560422013,30831727837091925,
%T 217363460829124577235,3903604149526204562445729
%N Number of (n+1) X (n+1) 0..2 arrays with every 2 X 2 subblock having the number of clockwise edge increases equal to the number of counterclockwise edge increases in its adjacent leftward and upward neighbors.
%C Diagonal of A206668.
%e Some solutions for n=4:
%e ..1..2..0..2..1....2..1..0..2..1....1..2..1..2..1....2..1..2..2..2
%e ..0..0..0..0..0....2..0..1..0..2....1..0..1..0..0....2..2..2..1..1
%e ..1..1..1..2..1....0..2..0..2..1....1..2..1..2..1....1..1..1..1..2
%e ..2..2..0..2..1....1..0..2..1..2....0..0..0..2..0....0..1..2..2..2
%e ..0..1..0..2..1....2..1..0..2..0....1..2..1..2..1....0..1..2..1..2
%K nonn
%O 1,1
%A _R. H. Hardin_, Feb 11 2012