

A189568


Number of permutations p of 1,2,...,n satisfying p(i+3)p(i)<>4 and p(j+4)p(j)<>3 for all i=1..n3, j=1..n4.


3



1, 1, 2, 6, 24, 80, 326, 1566, 9544, 65036, 518498, 4750006, 48830634, 554929274, 6926227324, 93970452970, 1377573324202
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OFFSET

0,3


COMMENTS

a(n) is also the number of ways to place n nonattacking pieces rook + leaper[3,4] on an n X n chessboard.


LINKS

Table of n, a(n) for n=0..16.
V. Kotesovec, Number of ways of placing nonattacking 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.
Sequence in context: A275206 A095110 A189858 * A002742 A048120 A322198
Adjacent sequences: A189565 A189566 A189567 * A189569 A189570 A189571


KEYWORD

nonn,more,hard


AUTHOR

Vaclav Kotesovec, Apr 23 2011


STATUS

approved



