Quartering a 2n X 2n chessboard (reference A257952) considering only the 90-deg rotationally symmetric results (omitting results with only 180-deg symmetry).

A064941

Quartering a 2n X 2n chessboard (reference A257952) considering only the 90-deg rotationally symmetric results (omitting results with only 180-deg symmetry).

Terms

    a(0) =1a(1) =3a(2) =26a(3) =596a(4) =38171a(5) =7083827a(6) =3852835452

External references