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

1,6

Comments

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

Links

Table of n, a(n) for n=1..40.

Tomás Oliveira e Silva, Enumeration of polyominoes

Crossrefs

Cf. A000104, A006747 (with holes allowed).

Sequence in context: A190728 A344435 A100791 * A006747 A184297 A108412

Adjacent sequences: A056880 A056881 A056882 * A056884 A056885 A056886

Keyword

nonn

Author

N. J. A. Sloane, Sep 03 2000

Extensions

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

Status

approved