Number of solutions to non-attacking rooks problem on n X n board that are invariant under 180-degree rotation.

A037223

Number of solutions to non-attacking rooks problem on n X n board that are invariant under 180-degree rotation.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =2a(4) =8a(5) =8a(6) =48a(7) =48a(8) =384a(9) =384a(10) =3840a(11) =3840a(12) =46080a(13) =46080a(14) =645120a(15) =645120a(16) =10321920a(17) =10321920a(18) =185794560a(19) =185794560a(20) =3715891200a(21) =3715891200a(22) =81749606400a(23) =81749606400

External references