# double factorial (Q13520655)

product of all the integers from 1 up to the integral input of the function that have the same parity as this input
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double factorial
product of all the integers from 1 up to the integral input of the function that have the same parity as this input

## Statements

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${\displaystyle n!!=\prod _{k=0}^{\left\lceil {\frac {n}{2}}\right\rceil -1}(n-2k)}$
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## Identifiers

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28 October 2013
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