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Factorial

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Tool for computing factorials. Factorial n! is the product of all integers numbers (not zero) inferior or equal to n, it is symbolized by an exclamation point juxtaposed after the number.

Factorial Calculator N!


Gamma Calculator Γ(N)


See also: Subfactorial

Answers to Questions

How to calculate a factorial?

Factorial of a number $ n $ is calculated with a multiplication: it is the product of the positive integers numbers (not null) less or equal to $ n $.

The usual notation to indicate a factorial is the exclamation mark positioned after the number. The factorial of $ n $ is noted $ n! $.

$$ n!=\prod_{k=1}^n k $$

Example: $$ 4! = 1 \times 2 \times 3 \times 4 = 24 $$

Example: The number of ways to sort a set of 52 cards is worth $ 52! = 1 \times 2 \times \dots \times 51 \times 52 = \\ 80658175170943878571660636856403766975289505440883277824000000000000 $$

Note that the factorial of zero is equal to one : $ 0! = 1 $

Example: Here are the values of the first factorials $$ 0! = 1 \\ 1! = 1 \\ 2! = 2 \\ 3! = 6 \\ 4! = 24 \\ 5! = 120 \\ 6! = 720 \\ 7! = 5040 \\ 8! = 40320 \\ 9! = 362880 \\ 10! = 3628800 $$

What is the Gamma Function?

Euler-Gamma is an extension of the factorial function over the complex numbers set. dCode offers calculation over the Reals. $$ \forall\,n \in \mathbb{N}, \; \Gamma(n+1)=n! $$

How to calculate a negative factorial?

Use the Gamma function.

How to quickly compute a factorial value?

For large numbers, it is possible to estimate the value of $ n! $ with a good precision using the Stirling formula. $$ n!\sim\sqrt{2\pi n}\left(\frac{n}{e}\right)^n $$

Source code

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