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%I #5 Mar 31 2012 12:37:29
%S 61,562,5075,46515,425803,3901194,35741496,327471411,3000373035,
%T 27490276714,251873944521,2307743577771,21144231048767,
%U 193729722925588,1775009260945536,16263162106133544,149007922275551448
%N 1/4 the number of (n+1)X4 0..3 arrays with every 2X2 subblock having exactly two distinct clockwise edge differences
%C Column 3 of A209553
%H R. H. Hardin, <a href="/A209548/b209548.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 15*a(n-1) -59*a(n-2) +27*a(n-3) +267*a(n-4) -488*a(n-5) +111*a(n-6) +312*a(n-7) -174*a(n-8) -30*a(n-9) +18*a(n-10) +2*a(n-11)
%e Some solutions for n=4
%e ..1..0..3..0....1..0..3..0....1..2..1..2....3..2..3..0....3..1..3..1
%e ..0..1..2..1....2..3..0..3....0..3..2..3....2..3..2..1....1..3..1..3
%e ..3..2..1..2....1..2..1..2....3..0..1..0....1..0..1..2....3..1..3..1
%e ..0..1..0..3....2..1..0..3....2..1..2..1....0..1..2..1....1..3..1..3
%e ..1..0..1..2....1..2..3..0....3..0..1..0....3..2..3..2....3..1..3..1
%K nonn
%O 1,1
%A _R. H. Hardin_ Mar 10 2012