Number of non-equivalent ways to place 3 non-attacking kings on an n X n board.

Terms

a(0) =0a(1) =0a(2) =2a(3) =20a(4) =138a(5) =505a(6) =1547a(7) =3759a(8) =8313a(9) =16350a(10) =30344a(11) =52470a(12) =87212a(13) =138255a(14) =212953a(15) =317065a(16) =461827a(17) =655724a(18) =915038a(19) =1251720a(20) =1688414a(21) =2241365a(22) =2941047a(23) =3808915a(24) =4884893a(25) =6196650a(26) =7795332a(27) =9715914a(28) =12022688a(29) =14759115