A210818 - OEIS

A210818

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

%I #6 Mar 07 2022 13:22:37

%S 0,47,18769,15675953,40094432569,349773663772607,10762101043733093559,

%T 1178656962552052684421464,460402167947340968868291699047,

%U 641654577152679219502203022480885713

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

%e Some solutions for n=3

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

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_, Mar 27 2012