Number of ways of placing n nonattacking superqueens on an n X n board.

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =0a(9) =4a(10) =44a(11) =156a(12) =1876a(13) =5180a(14) =32516a(15) =202900a(16) =1330622a(17) =8924976a(18) =64492432a(19) =495864256a(20) =3977841852a(21) =34092182276a(22) =306819842212