A057422 Axially symmetric (about axis 2) 2n-celled polyominoes with 1 hole.
0, 2, 4, 12, 24, 57, 112, 244, 483, 998, 1979
Offset: 4
Links
- Tomás Oliveira e Silva, Enumeration of polyominoes
Crossrefs
Cf. A056880.
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