A189877 Number of ways to place n nonattacking composite pieces queen + rider[2,4] on an n X n chessboard.

1, 0, 0, 2, 0, 0, 0, 0, 0, 4, 56, 172, 680, 1348, 6576, 34568, 107624, 413760, 1697288, 8035558, 37441416, 192483420, 1115143224

Offset

1,4

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>2k AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+2k<=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, A189874, A189876, A189855

Sequence in context: A170770 A107499 A123298 * A189868 A336104 A110981

Adjacent sequences: A189874 A189875 A189876 * A189878 A189879 A189880

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved