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Determine the number of its n-combinations

  1. Jan 27, 2008 #1
    Consider the multiset {n*a, n*b, 1, 2 , 3,..., n+1} of size 3n + 1. Determine the number of its n-combinations.

    I'm stuck on this one, any help would great.
     
  2. jcsd
  3. Jan 27, 2008 #2

    EnumaElish

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    How is its size 3n+1 and not n+3?
     
  4. Jan 27, 2008 #3
    Consider the case n=2

    you get

    (a,a,b,b 1,2,3) which gives you 7 elements

    not 5, so 3n + 1 holds.
     
  5. Jan 28, 2008 #4
    PRoblem solved, will this thread be deleted?
     
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