# FACTDOUBLE

FACTDOUBLE(number)

Returns the double factorial of a positive whole number.

 number The number you want the double factorial of.

 REMARKS
 * The double factorial is similar to the factorial, except it decrements by 2. * The double factorial of an even number is n*(n-2)*(n-4)...(4)*(2)* The double factorial of an odd number is n*(n-2)*(n-4)...(3)*(1)* The double factorial of 0 is 1.* If "number" < 0, then #NUM! is returned.* If "number" is not numeric, then #VALUE! is returned.* If "number" is even then, formula used is: n(n-2)(n-4) to (4)(2).* If "number" is odd then, formula used is: n(n-2)(n-4) to (3)(1).* You can use the FACT function to return the factorial of a positive whole number.* You can use the MULTINOMIAL function to return the factorial of the sum of values divided by the product of the values.* For the Microsoft documentation refer to support.microsoft.com* For the Google documentation refer to support.google.com

 A B 1 =FACTDOUBLE(0) = 1 = 0!! = 1 2 =FACTDOUBLE(1) = 1 = 1!! = 1 3 =FACTDOUBLE(2) = 2 = 2!! = 2 4 =FACTDOUBLE(3) = 3 = 3!! = 3*1 5 =FACTDOUBLE(4) = 8 = 4!! = 4*2 6 =FACTDOUBLE(5) = 15 = 5!! = 5*3*1 7 =FACTDOUBLE(6) = 48 = 6!! = 6*4*2 8 =FACTDOUBLE(7) = 105 = 7!! = 7*5*3*1 9 =FACTDOUBLE(4.1) = 8 10 =FACTDOUBLE(4.9) = 8 11 =FACTDOUBLE(-1) = 1 12 =FACTDOUBLE(-2) = #NUM!

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