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From: tenida@gmail.com
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Subject: compute (multimonial type) expression
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I need to compute what is the probability of selecting k balls from N
balls where ball j can be picked with prob p_j.

Prob (k balls are picked) = \sum_{i_1}^N \sum_{i_2, i_2 not equal to
i_1}^N......\sum_{i_k=1, i_k not equal to any of i_1,i_2,..,i_{k-1}}^N
p_{i_1} p_{i_2}...p_{i_k} \Prod_{j not equal to i_1, i_2, ..,i_k} (1-
p_j)


how can I compute Prob (k) efficiently, it seems there are N choose K
terms inside and for me N = 350 and K=10 ?

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