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

A210819

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