A189873 Number of ways to place n nonattacking composite pieces queen + rider[1,3] on an n X n chessboard.

1, 0, 0, 0, 0, 0, 0, 0, 0, 4, 56, 18, 116, 112, 408, 916, 2400, 7228, 27368, 111478, 445644, 1674860, 7624368, 38737270, 178933064

Offset

1,10

Comments

In fairy chess, the rider [1,3] is called a Camelrider.

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+k)-p(i)|<>3k AND |p(j+3k)-p(j)|<>k AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+k<=n, j+3k<=n, m+k<=n

Links

Table of n, a(n) for n=1..25.

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

Wikipedia, Fairy chess piece

Crossrefs

Cf. A102388, A189850

Sequence in context: A246968 A355073 A054751 * A358542 A359656 A329459

Adjacent sequences: A189870 A189871 A189872 * A189874 A189875 A189876

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved