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Homework Help: Conjugates in symmetric groups

  1. May 4, 2010 #1
    1. The problem statement, all variables and given/known data
    The question is, "How many conjugates does (1,2,3,4) have in S7?

    Another similar one -- how many does (1,2,3) have in S5?

    3. The attempt at a solution
    I know that the conjugates are all the elements with the same cycle structure, so for (123) I found there are 20 conjugates by hand listing them (132)...(354) etc. But I was wondering if there's some equation to find this amount- I haven't taken probability but I think there's got to be a statistical way to figure it out!! Thanks a lot.
  2. jcsd
  3. May 4, 2010 #2
    the binomial coefficient might be what you're looking for.
    "choose function"
  4. May 4, 2010 #3
    using the formula on (1,2,3) in S5, I got that it has 10 conjugates, which is wrong -- which N and R should I use for this example if not 5 and 3 (or am I calculating wrong)?
  5. May 4, 2010 #4
    No, you're doing it right (i.e. "this isn't what you're looking for). I forgot to divide by 2! (!)... :/
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