The OEIS is supported by the many generous donors to the OEIS Foundation.
%I #7 Dec 11 2015 21:30:14
%S 256,19688,3802676,5674969344,51975660472496,2363371012699739212
%N Number of (n+1) X (n+1) 0..3 arrays with every 2 X 2 subblock having the same number of clockwise edge increases as its horizontal neighbors and the same number of counterclockwise edge increases as its vertical neighbors.
%C Diagonal of A206188.
%e Some solutions for n=4:
%e ..0..2..1..1..0....3..1..3..2..1....3..1..1..3..3....1..3..1..0..0
%e ..3..1..3..2..1....3..1..3..2..0....0..1..2..3..1....3..3..1..3..3
%e ..0..1..2..2..0....3..3..3..3..3....1..3..3..2..1....1..1..1..2..2
%e ..1..3..1..3..1....2..3..0..0..1....1..2..3..1..1....0..3..2..0..3
%e ..3..1..0..0..2....0..3..2..1..2....3..1..1..3..2....3..3..2..3..3
%K nonn
%O 1,1
%A _R. H. Hardin_, Feb 04 2012