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%I #10 Aug 22 2017 20:53:08
%S 0,0,1,2,5,17,43,124,338,941,2591,7234,20125,56407,158349,446492,
%T 1262225,3580330,10181479,29031306,82968799,237642659,682014587,
%U 1960974220,5647919640,16292741605,47069104274
%N Number of primitive (period n) n-bead necklace structures using exactly three different colored beads.
%C Turning over the necklace is not allowed. Colors may be permuted without changing the necklace structure.
%D M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]
%F sum mu(d)*A056296(n/d) where d|n. Alternatively, A002075(n)-A000048(n)..
%Y Column 3 of A107424.
%Y Cf. A056288.
%K nonn
%O 1,4
%A _Marks R. Nester_
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