A189861 Number of ways to place n nonattacking composite pieces rook + rider[4,5] on an n X n chessboard.

1, 2, 6, 24, 120, 552, 2826, 17080, 117816, 943250, 7369128, 63533572, 603300392, 6280101222, 71927971040, 836503868762

Offset

1,2

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+4k)-p(i)|<>5k AND |p(j+5k)-p(j)|<>4k for all i>=1, j>=1, k>=1, i+4k<=n, j+5k<=n

Links

Table of n, a(n) for n=1..16.

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, A189852, A189856, A189859

Sequence in context: A263748 A072856 A228401 * A189570 A293775 A228399

Adjacent sequences: A189858 A189859 A189860 * A189862 A189863 A189864

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved