Sue is trying to make herself a necklace. She has 41 beads, each of which are a different colour. How many different necklaces can she make?
Arrangements with the same cyclic order are said to be the same.
A necklace is the same as another if you can flip one over to get the same necklace as the other.
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By the lemma that is not Burnside's , the number of orbits (i.e. different necklaces) under the action of the dihedral group D 4 1 (which has 41 rotations + 41 symmetries=82 elements) is:
N = ∣ D 4 1 ∣ 1 g ∈ D 4 1 ∑ F i x ( g )
The only element of D 4 1 which fixes some beads is the identity, because there are no two beads of the same colour, and there are 4 1 ! arrangements of the beads, so the answer is:
8 2 1 ⋅ 4 1 ! + 4 0 ⋅ 0 + 4 1 ⋅ 0 = 8 2 4 1 ! = 4 . 0 8 0 E 4 7