OFFSET
1,4
COMMENTS
An empress moves like a rook and a knight.
LINKS
V. Kotesovec, Non-attacking chess pieces
EXAMPLE
a(4) = 3: different ways to place 4 nonattacking empresses on a 4 X 4 board:
Xooo Xooo oXoo
oXoo oooX Xooo
ooXo ooXo oooX
oooX oXoo ooXo
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Witold Dlugosz, Oct 24 2012
STATUS
approved