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Homework Help: Combinatrics Problem

  1. Aug 11, 2005 #1
    I have this problem as follow

    prove that

    Summation of k=1 to n to the following term

    ( (-1)^(k+1) (( 2n-k) C ( k-1)) (4^(n-k))/k ) = ((4^n) - 1)/(2 n +1)

    Note that the symbol C above meant the symbol of combination .
  2. jcsd
  3. Aug 11, 2005 #2


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    I assume you mean:

    \sum_{k = 1}^{n} (-1)^{k+1} \binom{2n-k}{k-1} \frac{1}{k} 4^{n-k}
    = \frac{4^n - 1}{2n + 1}


    Have you tried anything? Or at least thought about how to begin, even if you weren't able to carry it through?
  4. Aug 11, 2005 #3
    Yes , I tried to do it using induction combined with Pascal's identity but it seems it does'nt work . Any suggestions how to go through ?
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