A327734 - OEIS

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).

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