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, 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

Offset: 2

Author

N. J. A. Sloane, Jul 17 2011

Keywords

• nonn

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.

Crossrefs

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

Cf. A000927.