%I #7 Jun 17 2022 14:43:05
%S 1,2,50,5280,1845589,2131393730,8110404963737,101713393925588269,
%T 4204356938900447492681,572796548087149263352167089,
%U 257205150385663723399847224344969
%N Number of n X n 0..3 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order.
%e Some solutions for n=4
%e ..0..1..0..1....0..1..0..1....0..1..2..3....0..1..2..1....0..1..3..0
%e ..1..2..3..1....1..2..3..3....1..0..1..0....1..0..1..3....1..2..0..3
%e ..0..3..1..0....0..3..1..2....2..1..0..1....2..1..0..2....3..0..1..3
%e ..1..1..0..1....1..3..2..3....3..0..1..2....1..3..2..1....0..3..3..0
%K nonn
%O 1,2
%A _R. H. Hardin_, Mar 29 2012
