A056880 Number of n-celled polyominoes without holes, symmetric about axis 2.

0, 1, 1, 1, 1, 2, 3, 4, 4, 6, 10, 11, 16, 18, 33, 34, 56, 56, 110, 106, 193, 177, 372, 335, 662, 571, 1269, 1084, 2282, 1875, 4365, 3568, 7914, 6257, 15141, 11935, 27615, 21170, 52911, 40486, 96980, 72490, 186144, 138981, 342638, 250814, 658884, 482029, 1217327, 875697, 2345272, 1686803

Offset

1,6

Comments

In other words, free polyominoes, without holes, with both vertical and horizontal symmetries but no other. - John Mason, Oct 10 2022

Links

Table of n, a(n) for n=1..52.

Tomás Oliveira e Silva, Enumeration of polyominoes

Crossrefs

Cf. A000104, A056877 (with holes allowed).

Sequence in context: A296116 A017832 A347713 * A053273 A347700 A049988

Adjacent sequences: A056877 A056878 A056879 * A056881 A056882 A056883

Keyword

nonn

Author

N. J. A. Sloane, Sep 03 2000

Extensions

a(29)-a(52) from John Mason, Oct 10 2022

Status

approved