A189878 Number of ways to place n nonattacking composite pieces queen + rider[2,5] on an n X n chessboard.

1, 0, 0, 2, 10, 4, 28, 20, 56, 72, 200, 644, 2940, 9152, 39200, 166100, 739924, 3586840, 18640500, 107580592, 547737844, 3080550788

Offset

1,4

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2k)-p(i)|<>5k AND |p(j+5k)-p(j)|<>2k AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+2k<=n, j+5k<=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, A189875, A189876, A189877, A189856

Sequence in context: A189872 A319407 A199832 * A189869 A054790 A140393

Adjacent sequences: A189875 A189876 A189877 * A189879 A189880 A189881

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved