Number of 4-cycles in the n X n rook complement graph.

Terms

a(0) =0a(1) =0a(2) =9a(3) =576a(4) =6900a(5) =44100a(6) =196245a(7) =686784a(8) =2023056a(9) =5232600a(10) =12224025a(11) =26310240a(12) =52936884a(13) =100663836a(14) =182452725a(15) =317318400a(16) =532407360a(17) =865571184a(18) =1368508041a(19) =2110550400a(20) =3183182100a(21) =4705372980a(22) =6829824309a(23) =9750223296a(24) =13709610000a(25) =19009965000a(26) =26023131225