A189854 Number of ways to place n nonattacking composite pieces rook + rider[2,3] on an n X n chessboard.

1, 2, 6, 12, 36, 174, 500, 2052, 12112, 65092, 407882, 2954798, 20568796, 157579774, 1346294112, 11580692142, 110130002110, 1145065547108

Offset

1,2

Comments

(in fairy chess the rider [2,3] is called a Zebrarider)

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

Links

Table of n, a(n) for n=1..18.

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: A120766 A121404 A202337 * A189565 A074442 A162589

Adjacent sequences: A189851 A189852 A189853 * A189855 A189856 A189857

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved