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A056877 Number of polyominoes with n cells, symmetric about axis 2. 13
0, 1, 1, 1, 1, 2, 3, 4, 4, 8, 10, 15, 17, 30, 35, 60, 64, 117, 128, 236, 241, 459, 476, 937, 912, 1813, 1789, 3706 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

This sequence counts polyominoes with exactly the symmetry group D_4 generated by horizontal and vertical reflections.

REFERENCES

D. H. Redelmeier, Counting polyominoes: yet another attack, Discrete Math., 36 (1981), 191-203.

LINKS

Table of n, a(n) for n=1..28.

Tomás Oliveira e Silva, Enumeration of polyominoes

D. H. Redelmeier, Table 3 of Counting polyominoes...

CROSSREFS

Cf. A000105, A001168, A006746, A056877, A006748, A056878, A006747, A006749.

Sequences classifying polyominoes by symmetry group: A000105, A006746, A006747, A006748, A006749, A056877, A056878, A142886, A144553, A144554.

Sequence in context: A224038 A241037 A097093 * A267232 A269606 A269640

Adjacent sequences:  A056874 A056875 A056876 * A056878 A056879 A056880

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane, Sep 03 2000

STATUS

approved

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Last modified December 2 15:01 EST 2016. Contains 278678 sequences.