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A327734 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
0, 0, 0, 0, 0, 0, 1, 2, 7, 12, 31, 57, 126, 232, 484, 900, 1800, 3388, 6643, 12594, 24457, 46624, 90157, 172680, 333498, 641088, 1238664, 2388357, 4620006, 8931052 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,8

LINKS

Table of n, a(n) for n=1..30.

EXAMPLE

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.

CROSSREFS

Column k=2 of A324802.

Cf. A056295, A056357.

Sequence in context: A102371 A007230 A290234 * A308706 A059053 A032025

Adjacent sequences:  A327731 A327732 A327733 * A327735 A327736 A327737

KEYWORD

nonn,more

AUTHOR

Andrew Howroyd, Sep 23 2019

STATUS

approved

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Last modified August 9 18:55 EDT 2022. Contains 356026 sequences. (Running on oeis4.)