`(n)! = prod_{:k=1:}^{ n :}k`

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The Factorial calculator computes the factorial of an positive integer.

INSTRUCTIONS: Enter the following:

• (n) This is a positive integer

Factorial (n!):  The calculator returns the factorial.

The Math / Science

The factorial equation is:

       `n! = prod_{:k=1:}^{n:}k`, which is the expression for 1•2•3• ... (n-2)•(n-1 )•n , where n must be a non-negative number.

For large numbers, factorial can be approximated using Stirling's factorial approximation.

Combinatorics Calculators

• n! - factorial
• `n!  sqrt(2 pi n) (n/e)^n` - Stirling's factorial approximation
• _nC_k - combinations
• C_r(n,k) - combinations with repetitions
• _nP_k - permutations
• P_r(n) - permutations with repetitions
• P_comp(n,2) - Comparison permutations
• P_c(n,r) - Circular Permutation