The ! Command

Command Summary

Calculates the factorial of a number or list.

Command Syntax

value!

Press:

1. MATH to access the math menu.
2. LEFT to access the PRB submenu.
3. 4 to select !, or use arrows.

TI-83/84/+/SE

1 byte

! is the factorial function, where n! = n*(n-1)! and 0! = 1, n an nonnegative integer. The function also works for arguments that are half an odd integer and greater than -1/2: $(-\frac1{2})!$ is defined as $\sqrt{\pi}$ and the rest are defined recursively.

3!
6
(‾.5)!
1.772453851
Ans²
3.141592654


The combinatorial interpretation of factorials is the number of ways to arrange n objects in order.

# Error Conditions

• ERR:DOMAIN for any numbers except the ones mentioned above.

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