Array read by antidiagonals: T(n,m) is the number of (directed) Hamiltonian paths in K_n X K_m.

Terms

a(0) =1a(1) =2a(2) =2a(3) =6a(4) =8a(5) =6a(6) =24a(7) =60a(8) =60a(9) =24a(10) =120a(11) =816a(12) =1512a(13) =816a(14) =120a(15) =720a(16) =17520a(17) =83520a(18) =83520a(19) =17520a(20) =720a(21) =5040a(22) =550080a(23) =8869680a(24) =22394880a(25) =8869680a(26) =550080a(27) =5040a(28) =40320a(29) =23839200