Number of 4-turn rook's tours on an n X n board summed over all starting positions.

Terms

a(0) =0a(1) =8a(2) =288a(3) =2208a(4) =9200a(5) =27720a(6) =68208a(7) =146048a(8) =282528a(9) =505800a(10) =851840a(11) =1365408a(12) =2101008a(13) =3123848a(14) =4510800a(15) =6351360a(16) =8748608a(17) =11820168a(18) =15699168a(19) =20535200a(20) =26495280a(21) =33764808a(22) =42548528a(23) =53071488a(24) =65580000a(25) =80342600a(26) =97651008