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A171011 Number of ways to place two non-attacking rooks on all free n-ominoes. 0
0, 0, 1, 9, 48, 242, 1178, 5793, 27651, 131383 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
LINKS
EXAMPLE
The triomino XX admits 1 combination of 2 non-attacking rooks.
............ X
CROSSREFS
Sequence in context: A054460 A115053 A181959 * A264273 A226751 A073584
KEYWORD
nonn
AUTHOR
David Scambler, Aug 27 2010
STATUS
approved

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Last modified March 19 04:26 EDT 2024. Contains 370952 sequences. (Running on oeis4.)