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A193179 Number of classes of two-dimensional generalized Bravais lattices with 2n-fold symmetry. 1
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1, 2, 9, 1, 9, 17, 1, 32, 1, 3, 34, 19, 2, 5, 121, 1, 211, 55, 1, 201, 695, 32, 43 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,22

COMMENTS

Related to class numbers of cyclotomic fields, although the precise relationship is not clear to me. Compare A000927.

REFERENCES

Mermin, N. David; Rokhsar, Daniel S.; and Wright, David C.; Beware of 46-fold symmetry: the classification of two-dimensional quasicrystallographic lattices.  Phys. Rev. Lett. 58 (1987), 2099-2101.

LINKS

Table of n, a(n) for n=2..49.

CROSSREFS

See A193175 for values of 2n such that a(n) = 1.

Cf. A000927.

Sequence in context: A083985 A109848 A104146 * A133705 A046111 A131779

Adjacent sequences:  A193176 A193177 A193178 * A193180 A193181 A193182

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Jul 17 2011

STATUS

approved

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Last modified April 16 12:16 EDT 2014. Contains 240591 sequences.