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A057425
Number of 2n-celled free polyominoes with 1 hole that have the 180-degree rotation symmetry and no others.
0
1, 7, 42, 193, 853, 3553, 14564, 58636, 234523, 931938
OFFSET
5,2
CROSSREFS
Cf. A056883.
Sequence in context: A212144 A266387 A008526 * A248329 A073376 A094429
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