Number of nX3 0..3 arrays with no more than floor(nX3/2) elements equal to at least one horizontal or vertical neighbor, with new values introduced in row major 0..3 order.

A222840

Number of nX3 0..3 arrays with no more than floor(nX3/2) elements equal to at least one horizontal or vertical neighbor, with new values introduced in row major 0..3 order.

Terms

    a(0) =2a(1) =105a(2) =4797a(3) =326408a(4) =15364848a(5) =1077545438a(6) =52487425596

External references