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%I #8 Mar 30 2012 16:52:03
%S 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,
%T 1,3,34,19,2,5,121,1,211,55,1,201,695,32,43
%N Number of classes of two-dimensional generalized Bravais lattices with 2n-fold symmetry.
%C Related to class numbers of cyclotomic fields, although the precise relationship is not clear to me. Compare A000927.
%D 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.
%Y See A193175 for values of 2n such that a(n) = 1.
%Y Cf. A000927.
%K nonn
%O 2,22
%A _N. J. A. Sloane_, Jul 17 2011
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