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A218244 Number of inequivalent (rotationally and reflectively distinct) ways to place n nonattacking empresses on n X n board. 2
1, 1, 1, 3, 6, 21, 75, 415, 2621, 21066, 195485, 2083543, 24744474, 323438322, 4596672672, 70440521310 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

An empress moves like a rook and a knight.

LINKS

Table of n, a(n) for n=1..16.

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

Cf. A137774, A002562.

Sequence in context: A294527 A261582 A135686 * A151961 A025229 A073951

Adjacent sequences:  A218241 A218242 A218243 * A218245 A218246 A218247

KEYWORD

nonn,more

AUTHOR

Witold Dlugosz, Oct 24 2012

STATUS

approved

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Last modified June 12 16:18 EDT 2021. Contains 344959 sequences. (Running on oeis4.)