Browse Definitions :
Definition

double factorial

The double factorial, symbolized by two exclamation marks (!!), is a quantity defined for all integer s greater than or equal to -1. For an even integer n , the double factorial is the product of all even integers less than or equal to n but greater than or equal to 2. For an odd integer p , the double factorial is the product of all odd integers less than or equal to p and greater than or equal to 1. The double factorial values of 0 and -1 are defined as equal to 1. Double factorial values for integers less than -1 are not defined.

Mathematically, the formulas for double factorial are as follows. If n is even, then

n !! = n ( n - 2)( n - 4)( n - 6) ... (4)(2)

If p is odd, then

p !! = p ( p - 2)( p - 4)( p - 6) ... (3)(1)

If q = 0 or q = -1, then q !! = 1 by convention.

The double factorial is mainly of interest to number theorists. It occasionally arises in statistics, combinatorics, calculus, and physics. Compare factorial .

This was last updated in September 2005

Continue Reading About double factorial

Start the conversation

Send me notifications when other members comment.

Please create a username to comment.

-ADS BY GOOGLE

File Extensions and File Formats

SearchCompliance

  • smart contract

    A smart contract, also known as a cryptocontract, is a computer program that directly controls the transfer of digital currencies...

  • risk map (risk heat map)

    A risk map, also known as a risk heat map, is a data visualization tool for communicating specific risks an organization faces. A...

  • internal audit (IA)

    An internal audit (IA) is an organizational initiative to monitor and analyze its own business operations in order to determine ...

SearchSecurity

SearchHealthIT

  • Health IT (health information technology)

    Health IT (health information technology) is the area of IT involving the design, development, creation, use and maintenance of ...

  • fee-for-service (FFS)

    Fee-for-service (FFS) is a payment model in which doctors, hospitals, and medical practices charge separately for each service ...

  • biomedical informatics

    Biomedical informatics is the branch of health informatics that uses data to help clinicians, researchers and scientists improve ...

SearchDisasterRecovery

  • risk mitigation

    Risk mitigation is a strategy to prepare for and lessen the effects of threats faced by a data center.

  • ransomware recovery

    Ransomware recovery is the process of resuming options following a cyberattack that demands payment in exchange for unlocking ...

  • natural disaster recovery

    Natural disaster recovery is the process of recovering data and resuming business operations following a natural disaster.

SearchStorage

  • RAID 5

    RAID 5 is a redundant array of independent disks configuration that uses disk striping with parity.

  • non-volatile storage (NVS)

    Non-volatile storage (NVS) is a broad collection of technologies and devices that do not require a continuous power supply to ...

  • petabyte

    A petabyte is a measure of memory or data storage capacity that is equal to 2 to the 50th power of bytes.

Close