A189855 Number of ways to place n nonattacking composite pieces rook + rider[2,4] on an n X n chessboard.

1, 2, 6, 24, 60, 208, 1184, 7840, 36036, 209664, 1395480, 10996728, 83573220, 723835856, 7132494776, 77976981216, 790552134804

Offset

1,2

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>2k for all i>=1, j>=1, k>=1, i+2k<=n, j+4k<=n

Links

Table of n, a(n) for n=1..17.

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, A189851, A189854, A189837

Sequence in context: A276838 A364424 A022917 * A189566 A178009 A357249

Adjacent sequences: A189852 A189853 A189854 * A189856 A189857 A189858

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved