Give a combinatorial proof that if n is a positive integer, then
\sum_{k=1}^{n} k\binom{n}{k}^...
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Mathematics, 24.08.2019 05:20 nauticatyson9
Give a combinatorial proof that if n is a positive integer, then
\sum_{k=1}^{n} k\binom{n}{k}^2= n\binom{2n-1}{n-1}
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