Number of Greek-key tours on a 6 X n grid.

Terms

a(0) =1a(1) =6a(2) =78a(3) =469a(4) =3501a(5) =22144a(6) =144476a(7) =899432a(8) =5585508a(9) =34092855a(10) =206571444a(11) =1241016042a(12) =7407467656a(13) =43975776229a(14) =259779839242