A057425 Number of 2n-celled free polyominoes with 1 hole that have the 180-degree rotation symmetry and no others.

1, 7, 42, 193, 853, 3553, 14564, 58636, 234523, 931938

Offset

5,2

Links

Table of n, a(n) for n=5..14.

Tomás Oliveira e Silva, Enumeration of polyominoes

Crossrefs

Cf. A056883.

Sequence in context: A212144 A266387 A008526 * A248329 A073376 A094429

Adjacent sequences: A057422 A057423 A057424 * A057426 A057427 A057428

Keyword

nonn,more

Author

N. J. A. Sloane, Sep 05 2000

Extensions

Name clarified, a(14) using data from Tomás Oliveira e Silva's website added by Andrei Zabolotskii, Sep 15 2025

Status

approved