Number of paths in Moebius ladder M_n.

Terms

a(0) =0a(1) =3a(2) =30a(3) =135a(4) =452a(5) =1295a(6) =3378a(7) =8295a(8) =19560a(9) =44847a(10) =100790a(11) =223223a(12) =488940a(13) =1061775a(14) =2289882a(15) =4910535a(16) =10480208a(17) =22275695a(18) =47178270a(19) =99605847a(20) =209704980a(21) =440390223a(22) =922733570a(23) =1929364775a(24) =4026514872