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Mathematica > Combinatorial Functions >

Factorial2 (!!)

n!!
gives the double factorial of n.
  • Mathematical function, suitable for both symbolic and numerical manipulation.
  • n!!=n(n-2)(n-4)⨯ ….
  • n!! is a product of even numbers for n even, and odd numbers for n odd.
  • Factorial2 can be evaluated to arbitrary numerical precision.
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