A189857 Number of ways to place n nonattacking composite pieces rook + rider[2,6] on an n X n chessboard.

1, 2, 6, 24, 120, 720, 2952, 16064, 104800, 816160, 7327728, 74031176, 621684168, 5950876288, 64694543120, 777746708096

Offset

1,2

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2k)-p(i)|<>6k AND |p(j+6k)-p(j)|<>2k for all i>=1, j>=1, k>=1, i+2k<=n, j+6k<=n

Links

Table of n, a(n) for n=1..16.

V. Kotesovec, Number of ways of placing non-attacking queens, kings, bishops and knights (in English and Czech)

Wikipedia, Fairy chess piece

Crossrefs

Cf. A000170, A189854, A189855, A189856, A189853

Sequence in context: A364426 A178011 A189853 * A189860 A274795 A174702

Adjacent sequences: A189854 A189855 A189856 * A189858 A189859 A189860

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved