That'll be a colourful necklace

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?


Details and Assumptions:

  1. Arrangements with the same cyclic order are said to be the same.

  2. A necklace is the same as another if you can flip one over to get the same necklace as the other.


The answer is 4.080E+47.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

3 solutions

Emmanuel Lasker
Oct 14, 2014

By the lemma that is not Burnside's , the number of orbits (i.e. different necklaces) under the action of the dihedral group D 41 D_{41} (which has 41 rotations + 41 symmetries=82 elements) is:

N = 1 D 41 g D 41 F i x ( g ) N= \displaystyle \frac{1}{|D_{41}|}\sum_{g\in D_{41}} Fix(g)

The only element of D 41 D_{41} which fixes some beads is the identity, because there are no two beads of the same colour, and there are 41 ! 41! arrangements of the beads, so the answer is:

1 41 ! + 40 0 + 41 0 82 = 41 ! 82 = 4.080 E 47 \frac{1\cdot 41!+40\cdot 0+41\cdot 0}{82}=\frac{41!}{82}=\boxed{4.080E47}

(n-1)!/2

n=> no of beads to form a necklace

Vivek Sedani
Oct 9, 2014

Number of possible different necklaces =( (41!) / ( 41 ) ) / 2

I think you mean 41!/41, not 40.

Sharky Kesa - 6 years, 8 months ago

Log in to reply

Oh ya! Thank you for pointing it out!! . It is now updated.

vivek sedani - 6 years, 8 months ago

u r right @Sharky Kesa

subham jyoti mishra - 6 years, 8 months ago

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...