Number of ways to place 3 nonattacking kings on an n X n board.

Terms

a(0) =0a(1) =0a(2) =0a(3) =8a(4) =140a(5) =964a(6) =3920a(7) =11860a(8) =29708a(9) =65240a(10) =129984a(11) =240240a(12) =418220a(13) =693308a(14) =1103440a(15) =1696604a(16) =2532460a(17) =3684080a(18) =5239808a(19) =7305240a(20) =10005324a(21) =13486580a(22) =17919440a(23) =23500708a(24) =30456140a(25) =39043144a(26) =49553600a(27) =62316800