Number of Hamiltonian paths in P_3 X P_n.

Terms

a(0) =1a(1) =8a(2) =20a(3) =62a(4) =132a(5) =336a(6) =688a(7) =1578a(8) =3190a(9) =6902a(10) =13878a(11) =29038a(12) =58238a(13) =119518a(14) =239390a(15) =485822a(16) =972414a(17) =1960830a(18) =3923326a(19) =7882494a(20) =15768574a(21) =31616510a(22) =63240702a(23) =126655486a(24) =253327358a(25) =507033598a(26) =1014102014a(27) =2029023230a(28) =4058120190a(29) =8118001662