

A006748


Number of diagonally symmetric polyominoes with n cells.
(Formerly M0366)


13



0, 0, 1, 0, 2, 2, 7, 5, 26, 22, 91, 79, 326, 301, 1186, 1117, 4352, 4212, 16119, 15849, 60174, 60089, 226146, 228426, 854803, 872404, 3247207, 3342579
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OFFSET

1,5


COMMENTS

This sequence counts polyominoes with exactly the symmetry group of order 2 generated by a single reflection about a diagonal.


REFERENCES

D. H. Redelmeier, Counting polyominoes: yet another attack, Discrete Math., 36 (1981), 191203.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Table of n, a(n) for n=1..28.
Tomas Oliveira e Silva, Enumeration of polyominoes
D. H. Redelmeier, Table 3 of Counting polyominoes...


CROSSREFS

Cf. A000105, A001168, A006746, A056877, A006748, A056878, A006747.
Sequences classifying polyominoes by symmetry group: A000105, A006746, A006747, A006748, A006749, A056877, A056878, A142886, A144553, A144554.
Sequence in context: A249493 A223000 A058625 * A193548 A131049 A126851
Adjacent sequences: A006745 A006746 A006747 * A006749 A006750 A006751


KEYWORD

nonn


AUTHOR

N. J. A. Sloane.


EXTENSIONS

Extended to n=28 by Tomas Oliveira e Silva.


STATUS

approved



