A189868 Number of ways to place n nonattacking composite pieces queen + leaper[2,4] on an n X n chessboard.

1, 0, 0, 2, 0, 0, 0, 0, 0, 4, 64, 384, 2936, 10720, 62664, 420272, 2540584, 16373760, 115200080, 868564232, 6708291360

Offset

1,4

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2)-p(i)|<>4 AND |p(j+4)-p(j)|<>2 AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+2<=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, A189867, A189566

Sequence in context: A107499 A123298 A189877 * A336104 A110981 A019261

Adjacent sequences: A189865 A189866 A189867 * A189869 A189870 A189871

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved