A189567 Number of permutations p of 1,2,...,n satisfying |p(i+2)-p(i)|<>5 and |p(j+5)-p(j)|<>2 for all i=1..n-2, j=1..n-5.

1, 1, 2, 6, 24, 120, 392, 1810, 10400, 72228, 589674, 5196870, 52398658, 588036216, 7274466172, 98024173852, 1427556373892

Offset

0,3

Comments

a(n) is also the number of ways to place n nonattacking pieces rook + leaper[2,5] on an n X n chessboard.

Links

Table of n, a(n) for n=0..16.

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.

Sequence in context: A330043 A062348 A189856 * A189859 A189569 A174701

Adjacent sequences: A189564 A189565 A189566 * A189568 A189569 A189570

Keyword

nonn,more,hard

Author

Vaclav Kotesovec, Apr 23 2011

Status

approved