Returns the double factorial of a number: FACTDOUBLE(number)
Number is the value for which to return the double factorial. If number is not an integer, it is truncated.
Remarks
If number is nonnumeric, FACTDOUBLE returns the #VALUE! error value.
If number is negative, FACTDOUBLE returns the #NUM! error value.
Has a cache for more speed of previously calculated factorial
Add additional sanity check/integration test FormulaEvalTestData.xls
git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1530907 13f79535-47bb-0310-9956-ffa450edef68
