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A057424
Diagonally symmetric (about diagonal 2) 2n-celled polyominoes with 1 hole.
0
1, 1, 5, 7, 21, 30, 88, 116, 336, 439, 1271, 1639, 4713, 6088, 17452
(list; graph; refs; listen; history; text; internal format)
OFFSET
6,3
COMMENTS
The sequence refers to polyominoes with one hole and both diagonal symmetries but no other. - John Mason, Jan 16 2023
LINKS
Table of n, a(n) for n=6..20.
Tomás Oliveira e Silva, Enumeration of polyominoes
CROSSREFS
Cf. A056882.
Sequence in context: A120035 A198302 A091154 * A027152 A076197 A002596
Adjacent sequences: A057421 A057422 A057423 * A057425 A057426 A057427
KEYWORD
nonn,more
AUTHOR
N. J. A. Sloane, Sep 05 2000
EXTENSIONS
a(15)-a(20) from John Mason, Jan 16 2023
STATUS
approved

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Last modified February 26 02:50 EST 2025. Contains 381215 sequences.
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