A189874 Number of ways to place n nonattacking composite pieces queen + rider[1,4] on an n X n chessboard.

1, 0, 0, 2, 10, 0, 0, 4, 8, 28, 100, 186, 624, 1720, 7288, 30666, 100220, 360208, 1517804, 7302336, 29429672, 139854636, 753288744

Offset

1,4

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 AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+k<=n, j+4k<=n, m+k<=n

Links

Table of n, a(n) for n=1..23.

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, A189873, A189851

Sequence in context: A189875 A189866 A364253 * A189865 A189880 A189871

Adjacent sequences: A189871 A189872 A189873 * A189875 A189876 A189877

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved