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A171009 Number of ways to place two non-attacking queens on all free n-ominoes. 0
0, 0, 0, 2, 21, 131, 733, 3882, 19641, 97282 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

The pentomino XXXX admits 2 combinations of 2 non-attacking queens.

............. X

CROSSREFS

Sequence in context: A091789 A109789 A136588 * A098661 A095262 A209519

Adjacent sequences:  A171006 A171007 A171008 * A171010 A171011 A171012

KEYWORD

nonn

AUTHOR

David Scambler, Aug 27 2010

STATUS

approved

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Last modified October 31 08:46 EDT 2020. Contains 338101 sequences. (Running on oeis4.)