Number of ways to place 2 queens on an n X n chessboard so that they attack each other.

Terms

a(0) =0a(1) =6a(2) =28a(3) =76a(4) =160a(5) =290a(6) =476a(7) =728a(8) =1056a(9) =1470a(10) =1980a(11) =2596a(12) =3328a(13) =4186a(14) =5180a(15) =6320a(16) =7616a(17) =9078a(18) =10716a(19) =12540a(20) =14560a(21) =16786a(22) =19228a(23) =21896a(24) =24800a(25) =27950a(26) =31356a(27) =35028a(28) =38976a(29) =43210