Number of 2nX2n 0..3 arrays with values 0..3 introduced in row major order and each element equal to exactly two horizontal and vertical neighbors.

A198597

Number of 2nX2n 0..3 arrays with values 0..3 introduced in row major order and each element equal to exactly two horizontal and vertical neighbors.

Terms

    a(0) =1a(1) =5a(2) =674a(3) =844228a(4) =8055413256

External references