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Factorial Notation

If nn is a positive integer, then the factorial of nn, written in factorial notation as n!n!, is defined as the product of all positive integers less than or equal to nn: n!=n(n1)(n2)(3)(2)(1)n! = n(n-1)(n-2)\dots(3)(2)(1). By definition, the value of 0!0! is 11.

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Updated 2026-05-25

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