Number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having one or two distinct values, and new values 0..3 introduced in row major order.

A209841

Number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having one or two distinct values, and new values 0..3 introduced in row major order.