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Number of n-bead bracelet structures using exactly two different colored beads that are not self-equivalent under either a nonzero rotation or reversal (turning over bracelet).
2

%I #5 Sep 23 2019 20:31:36

%S 0,0,0,0,0,0,1,2,7,12,31,57,126,232,484,900,1800,3388,6643,12594,

%T 24457,46624,90157,172680,333498,641088,1238664,2388357,4620006,

%U 8931052

%N Number of n-bead bracelet structures using exactly two different colored beads that are not self-equivalent under either a nonzero rotation or reversal (turning over bracelet).

%e Case n=7: There are 7 necklace structures using exactly two colors. See example in A056295. Of these, 5 are achiral and the other two a chiral pair: AAABABB/AAABBAB. a(7) = 1, since this sequence considers chiral pairs as the same bracelet structure.

%Y Column k=2 of A324802.

%Y Cf. A056295, A056357.

%K nonn,more

%O 1,8

%A _Andrew Howroyd_, Sep 23 2019