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 Documentation / Mathematica / Built-in Functions / Mathematical Functions / Factorial Related  /
Factorial2

  • n !! gives the double factorial of n.
  • Mathematical function (see Section A.3.10).
  • .
  • is a product of even numbers for even, and odd numbers for odd.
  • See the Mathematica book: Section 3.2.5.
  • See also: Gamma.

    Further Examples

    Here is a table of the first 20 double factorials.

    In[1]:=

    Out[1]//TableForm=