A210833 - OEIS

%I #4 Mar 31 2012 12:37:34

%S 3,33,798,39272,3683671,640787121,204615573204,119576103350570,

%T 127795340782521808,249802991080797461268

%N Number of (n+1)X(n+1) 0..3 symmetric matrices with every 2X2 subblock having two or four distinct values, and new values 0..3 introduced in lower triangle row major order

%e Some solutions for n=3

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

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

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

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

%K nonn

%O 1,1

%A _R. H. Hardin_ Mar 27 2012