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A056883
Number of n-celled rotationally symmetric polyominoes without holes.
3
0, 0, 0, 1, 1, 5, 4, 18, 19, 72, 72, 268, 276, 1002, 1043, 3733, 3926, 14000, 14810, 52658, 55987, 199020, 212364, 754826, 807861, 2872926, 3082202, 10966333, 11789248, 41970489, 45198317, 160996986, 173640109, 618839771, 668316169, 2383000591, 2576516523, 9191269314, 9947949563, 35502661446
OFFSET
1,6
COMMENTS
In other words, free unholey polyominoes with 180-degree rotational symmetry and no other. - John Mason, Oct 11 2022
CROSSREFS
Cf. A000104, A006747 (with holes allowed).
Sequence in context: A190728 A344435 A100791 * A006747 A184297 A108412
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 03 2000
EXTENSIONS
a(29)-a(40) from John Mason, Oct 11 2022
STATUS
approved