Number of ways to reciprocally link elements of an 2 X n array either to themselves or to exactly two horizontal, diagonal and antidiagonal neighbors, without consecutive collinear links.

A220739

Number of ways to reciprocally link elements of an 2 X n array either to themselves or to exactly two horizontal, diagonal and antidiagonal neighbors, without consecutive collinear links.

Terms

    a(0) =1a(1) =2a(2) =5a(3) =13a(4) =32a(5) =85a(6) =221a(7) =578a(8) =1513a(9) =3961a(10) =10368a(11) =27145a(12) =71065a(13) =186050a(14) =487085a(15) =1275205a(16) =3338528a(17) =8740381a(18) =22882613a(19) =59907458a(20) =156839761a(21) =410611825a(22) =1074995712a(23) =2814375313a(24) =7368130225a(25) =19290015362a(26) =50501915861a(27) =132215732221

External references