Number of non-attacking placements of 3 rooks on an n X n board.

Terms

a(0) =0a(1) =0a(2) =6a(3) =96a(4) =600a(5) =2400a(6) =7350a(7) =18816a(8) =42336a(9) =86400a(10) =163350a(11) =290400a(12) =490776a(13) =794976a(14) =1242150a(15) =1881600a(16) =2774400a(17) =3995136a(18) =5633766a(19) =7797600a(20) =10613400a(21) =14229600a(22) =18818646a(23) =24579456a(24) =31740000a(25) =40560000a(26) =51333750a(27) =64393056a(28) =80110296