A056883 Number of n-celled rotationally symmetric polyominoes without holes.

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

Author

N. J. A. Sloane, Sep 03 2000

Keywords

• nonn

Comments

In other words, free unholey polyominoes with 180-degree rotational symmetry and no other. - John Mason, Oct 11 2022

Links

• Tomás Oliveira e Silva, Enumeration of polyominoes

Crossrefs

Cf. A000104, A006747 (with holes allowed).

Extensions

a(29)-a(40) from John Mason, Oct 11 2022