A189569 Number of permutations p of 1,2,...,n satisfying |p(i+3)-p(i)|<>5 and |p(j+5)-p(j)|<>3 for all i=1..n-3, j=1..n-5.

1, 1, 2, 6, 24, 120, 464, 2274, 13236, 91760, 740562, 6541984, 65632694, 732880076, 8995905626, 120367234946

Offset

0,3

Comments

a(n) is also the number of ways to place n nonattacking pieces rook + leaper[3,5] on an n X n chessboard.

Links

Table of n, a(n) for n=0..15.

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

Formula

Asymptotic: a(n)/n! ~ 1/e^4.

Crossrefs

Cf. A137774, A189358, A189563, A189564, A189565, A189566, A189567, A189568.

Sequence in context: A189856 A189567 A189859 * A174701 A178848 A173845

Adjacent sequences: A189566 A189567 A189568 * A189570 A189571 A189572

Keyword

nonn,more,hard

Author

Vaclav Kotesovec, Apr 23 2011

Status

approved