double factorials

A form of double factorial — For an odd integer, the result of multiplying all the odd integers from 1 to the given number; or for an even integer, the result of multiplying all the even integers from 2 to the given number; symbolised by a double exclamation mark (!!). For example, 9!! = 1 × 3 × 5 × 7 × 9 = 945.

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Meanings

noun
  1. pluralplural of double factorial
Cite this entry
APA

double factorials. (n.d.). In WatkinsX Dictionary. Retrieved November 4, 2026, from https://dictionary.watkinsx.com/word/double%20factorials

MLA

“double factorials.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/double%20factorials. Accessed November 4, 2026.

Chicago

WatkinsX Dictionary, s.v. “double factorials,” accessed November 4, 2026, https://dictionary.watkinsx.com/word/double%20factorials.

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