Number of ways to reciprocally link elements of an n X 3 array either to themselves or to exactly two horizontal, diagonal and antidiagonal neighbors, without consecutive collinear links.

A220733

Number of ways to reciprocally link elements of an n X 3 array either to themselves or to exactly two horizontal, diagonal and antidiagonal neighbors, without consecutive collinear links.

Terms

    a(0) =1a(1) =5a(2) =22a(3) =72a(4) =258a(5) =949a(6) =3403a(7) =12241a(8) =44192a(9) =159272a(10) =573952a(11) =2069009a(12) =7457849a(13) =26881189a(14) =96893542a(15) =349253376a(16) =1258880466a(17) =4537629845a(18) =16355874451a(19) =58954682593a(20) =212501925632a(21) =765962408016

External references