A189879 Number of ways to place n nonattacking composite pieces queen + rider[3,4] on an n X n chessboard.

1, 0, 0, 2, 2, 4, 28, 0, 20, 20, 180, 520, 1888, 6016, 22480, 105236, 433500, 1933604, 9687268, 50998366, 269523272, 1507984008

Offset

1,4

Comments

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

Links

Table of n, a(n) for n=1..22.

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, A189877, A189858

Sequence in context: A098335 A346714 A049147 * A189870 A257614 A067068

Adjacent sequences: A189876 A189877 A189878 * A189880 A189881 A189882

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved