Number of nX4 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without move-in move-out left turns.

A221733

Number of nX4 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without move-in move-out left turns.

Terms

    a(0) =21a(1) =1347a(2) =89920a(3) =5962648a(4) =394328064a(5) =26082119800

External references