Number of ways to reciprocally link elements of an n X 3 array either to themselves or to exactly one horizontal, diagonal and antidiagonal neighbor.

A220616

Number of ways to reciprocally link elements of an n X 3 array either to themselves or to exactly one horizontal, diagonal and antidiagonal neighbor.

Terms

    a(0) =3a(1) =21a(2) =125a(3) =765a(4) =4657a(5) =28373a(6) =172833a(7) =1052829a(8) =6413369a(9) =39067429a(10) =237981569a(11) =1449678893a(12) =8830805161a(13) =53793374581a(14) =327685538769

External references