Number of (undirected) Hamiltonian paths in the 2n-crossed prism graph.

Terms

a(0) =72a(1) =288a(2) =960a(3) =2880a(4) =8064a(5) =21504a(6) =55296a(7) =138240a(8) =337920a(9) =811008a(10) =1916928a(11) =4472832a(12) =10321920a(13) =23592960a(14) =53477376a(15) =120324096a(16) =268959744a(17) =597688320a(18) =1321205760a(19) =2906652672a(20) =6366953472a(21) =13891534848a(22) =30198988800a(23) =65431142400a(24) =141331267584a(25) =304405807104