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Help: Multiple summation problem

Please help in computing the following summation.

\[\large \mathop{\sum\sum\sum\sum}_{0 \leq i < j < k < l\leq n } 2 \]

The answer to this is \(2 \dbinom{ n+1 }{4} \).

Note by Swagat Panda
4 months, 2 weeks ago

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The given sum is just twice the ways of ways of picking integers \(i, j, k, l\) with the constraint that \(0\leq i<j<k<l\leq n\) which is just \[2 {n+1 \choose 4} \] Deeparaj Bhat · 4 months, 2 weeks ago

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@Deeparaj Bhat thank you very much Swagat Panda · 4 months, 2 weeks ago

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