OFFSET
0,3
COMMENTS
a(n) is also the number of ways to place n nonattacking pieces rook + leaper[4,5] on an n X n chessboard.
LINKS
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
KEYWORD
nonn,more,hard
AUTHOR
Vaclav Kotesovec, Apr 23 2011
STATUS
approved