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A057425
Number of rotationally symmetric 2n-celled polyominoes with 1 hole.
0
1, 7, 42, 193, 853, 3553, 14564, 58636, 234523
OFFSET
5,2
CROSSREFS
Cf. A056883.
Sequence in context: A212144 A266387 A008526 * A248329 A073376 A094429
KEYWORD
nonn,more
AUTHOR
N. J. A. Sloane, Sep 05 2000
STATUS
approved