Intro to Algebra, Symmetric group # of elements of order 4 in S6

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SUMMARY

The discussion focuses on calculating the number of elements of order 4 in the symmetric group S6. The key forms identified are the 4-cycles (abcd) and the 4+2 cycles (abcd)(ef). With a total of 720 elements in S6, the calculation begins by selecting 4 elements from 6, which is a combinatorial problem. The distinct 4-cycles can be derived from the permutations of the chosen elements, leading to a systematic approach for counting both pure 4-cycles and 4+2 cycles.

PREREQUISITES
  • Understanding of symmetric groups, specifically S6
  • Knowledge of permutations and cycle notation
  • Familiarity with combinatorial selection (binomial coefficients)
  • Basic concepts of group theory and element orders
NEXT STEPS
  • Research the properties of symmetric groups, focusing on S6
  • Learn about cycle types and their significance in group theory
  • Study combinatorial methods for selecting subsets from larger sets
  • Explore the concept of element orders in abstract algebra
USEFUL FOR

This discussion is beneficial for students of abstract algebra, mathematicians studying group theory, and anyone interested in combinatorial mathematics and permutations.

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Homework Statement



How many elements of order 4 are in S6? (symmetric group with order 6)

Homework Equations





The Attempt at a Solution



So, the different forms of elements with order 4 in S6 are

(abcd)(ef), (abcd)

from there I am sunk on how to calculate. I know there are 6! = 720 total elements in S6.
 
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well, first, how many 4-cycles are there?

first, we have to pick 4 elements to permute out of 6. how many ways are there to choose 4 elements out of 6?

let's say we've picked our 4: {a,b,c,d}.

how many distinct 4-cycles can you make on that set (this should be the same number of 4-cycles as we have in S4, right?).

that should help you with the "pure" 4 -cycles.

now, suppose you have (a b c d)(e f).

once we've chosen a,b,c,d (step one in counting the 4-cycles), do we really have any choice as how to choose e and f? and given any two elements of {1,2,3,4,5,6}, say, j and k, how many transpositions can be made from j and k? if you think about this the right way, you don't even have to count the 4+2 cycles.
 

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