A189851 Number of ways to place n nonattacking composite pieces rook + rider[1,4] on an n X n chessboard.

1, 2, 6, 24, 48, 182, 868, 5752, 22952, 131766, 912964, 7556978, 52602390, 432795244, 4121203656, 44335718598, 416447624724

Offset

1,2

Comments

In fairy chess, the rider [1,4] is called a Girafferider.

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>k for all i>=1, j>=1, k>=1, i+k<=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, A189837, A189850

Sequence in context: A113904 A099144 A354216 * A189563 A321613 A104114

Adjacent sequences: A189848 A189849 A189850 * A189852 A189853 A189854

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved