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A171010
Number of ways to place two non-attacking kings on all free n-ominoes.
0
0, 0, 1, 7, 46, 240, 1207, 6004, 28903, 137996
OFFSET
1,4
EXAMPLE
E.g. the triomino XXX admits 1 combination of 2 non-attacking kings.
CROSSREFS
Sequence in context: A175909 A034471 A100024 * A258630 A264201 A086092
KEYWORD
nonn
AUTHOR
David Scambler, Aug 27 2010
STATUS
approved