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Results tagged with co.combinatorics
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user 121775
Enumerative combinatorics, graph theory, order theory, posets, matroids, designs and other discrete structures. It also includes algebraic, analytic and probabilistic combinatorics.
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How to prove the combinatorial equality? [closed]
Please, help me to understand following convolution (or give a reference):
$$
\sum_{R=0}^N \binom{R}{r} \binom{N-R}{n-r} = \binom{N+1}{n+1}
$$
Why is it true?
Thank you!
