A189870 Number of ways to place n nonattacking composite pieces queen + leaper[3,4] on an n X n chessboard.

1, 0, 0, 2, 2, 4, 28, 0, 20, 52, 280, 1192, 5520, 20196, 115936, 701836, 4174032, 27261284, 193428616, 1445733328, 11133210948

Offset

1,4

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+3)-p(i)|<>4 AND |p(j+4)-p(j)|<>3 AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+3<=n, j+4<=n, m+k<=n

Links

Table of n, a(n) for n=1..21.

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

Wikipedia, Fairy chess piece

Crossrefs

Cf. A051223, A189865, A189868, A189568

Sequence in context: A346714 A049147 A189879 * A257614 A067068 A290126

Adjacent sequences: A189867 A189868 A189869 * A189871 A189872 A189873

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved