%I #9 Oct 03 2025 15:29:05

%S 3520628,2641341716,1896474527890,1410846309824300,

%T 1043428174053823487,774627496109684203370,574519716040871948229631,

%U 426321464405769045098450336,316304017251899250835605915141

%N Half the number of (n+1)X7 0..3 arrays with every 2X2 subblock having exactly one duplicate clockwise edge difference.

%C Column 6 of A209787

%H R. H. Hardin, <a href="/A209785/b209785.txt">Table of n, a(n) for n = 1..210</a>

%e Some solutions for n=4

%e ..3..3..3..0..1..1..1....1..2..1..1..0..0..1....1..1..2..2..1..0..0

%e ..1..3..0..0..0..2..2....0..0..3..1..1..0..0....3..1..0..1..1..1..0

%e ..2..3..3..3..0..0..1....3..3..3..1..2..0..1....3..1..0..0..2..1..1

%e ..3..3..2..1..2..2..1....3..2..3..1..0..0..1....3..1..0..1..1..1..2

%e ..3..2..2..2..2..3..3....1..1..3..1..1..0..0....3..2..2..1..0..0..0

%K nonn

%O 1,1

%A _R. H. Hardin_, Mar 13 2012