%I
%S 1,3,70,6516,1741480,1297416720,2686765690144,15449867954722880
%N Number of (2n)X(2n) 0..3 symmetric matrices with every element equal to two horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order
%e All solutions for n=2
%e ..0..0..1..1....0..0..1..1....0..0..0..0
%e ..0..0..1..1....0..0..1..1....0..1..1..0
%e ..1..1..2..2....1..1..0..0....0..1..1..0
%e ..1..1..2..2....1..1..0..0....0..0..0..0
%K nonn
%O 1,2
%A _R. H. Hardin_ Mar 29 2012
