A189850 Number of ways to place n nonattacking composite pieces rook + rider[1,3] on an n X n chessboard.

1, 2, 6, 8, 24, 126, 316, 1344, 7782, 33930, 172430, 1106754, 6432236, 45188572, 372437930, 2728674526, 23648822368, 233010291526, 2083328647344

Offset

1,2

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 for all i>=1, j>=1, k>=1, i+k<=n, j+3k<=n

Links

Table of n, a(n) for n=1..19.

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

Sequence in context: A193946 A349259 A349260 * A189358 A116083 A115506

Adjacent sequences: A189847 A189848 A189849 * A189851 A189852 A189853

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved