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=FACTDOUBLE(N)=
=FACTDOUBLE(Number)=
*where, <math>N</math> is a positive integer whose double factorial is to be found.
*<math>Number</math> is a positive integer whose double factorial is to be found.
FACTDOUBLE(), returns the double factorial of a number.
== Description ==
== Description ==
FACTDOUBLE(N)
FACTDOUBLE(Number)
e.g. FACTDOUBLE(6) displays '''48''' as a result.
e.g. FACTDOUBLE(6) displays '''48''' as a result.
*<math>N</math> should be a positive integer.
*<math>Number</math> should be a positive integer.
*The factorial of an even number is calculated as -
*The factorial of an even number is calculated as -
<math>N!! = N * (N-2) * (N-4) * .....3 * 1</math>
<math>N!! = N * (N-2) * (N-4) * .....3 * 1</math>
*If <math>N</math> is negative, Calci displays #N/A error message.
*If <math>Number</math> is negative, Calci displays #N/A error message.
*If <math>N</math> is not an integer, it is truncated to calculate the double factorial.
*If <math>Number</math> is not an integer, it is truncated to calculate the double factorial.
*If <math>N</math> is invalid, Calci displays #NULL error message.
*If <math>Number</math> is invalid, Calci displays #NULL error message.
*The double factorial of series of numbers can be calculated as -
*The double factorial of series of numbers can be calculated as -
e.g. FACTDOUBLE(1..5) calculates double factorial of numbers from 1 to 5 and displays result as '''1 2 3 8 15'''.
e.g. FACTDOUBLE(1..5) calculates double factorial of numbers from 1 to 5 and displays result as '''1 2 3 8 15'''.