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%I #9 Oct 06 2015 21:46:00
%S 57,4995,2071311,4099186545,38883961392081,1772313933013227273,
%T 388756746462464273412765,410796134340987241848792211659,
%U 2092643007412378548345728130194640495
%N Number of (n+1) X (n+1) 0..2 arrays with the number of clockwise edge increases in every 2 X 2 subblock equal to the number of counterclockwise edge increases.
%C Diagonal of A209517.
%H R. H. Hardin, <a href="/A209512/b209512.txt">Table of n, a(n) for n = 1..10</a>
%e Some solutions for n=4:
%e ..1..2..0..0..1....2..1..0..2..2....1..0..0..0..0....0..1..2..2..0
%e ..0..1..2..2..0....0..2..1..0..0....1..0..1..0..0....0..0..1..1..2
%e ..0..1..1..1..2....1..0..2..1..0....2..1..0..2..2....2..0..1..0..1
%e ..1..1..2..1..1....2..1..0..2..1....2..1..1..0..2....0..2..0..1..2
%e ..1..2..2..2..1....2..1..1..0..2....2..1..1..0..2....0..0..2..0..1
%K nonn
%O 1,1
%A _R. H. Hardin_, Mar 09 2012