Permutations and Combinations


   
 
Factorial Notation
Let n be a positive integer. The continued product of first n natural numbers is called factorial n and is denoted as n!.
 
Note:
 
1. O!= 1
 
2. When n is a negative or fraction, n! is not defined.
 
 
Examples:
 
8! = 8 x 7 x 6 x 5 x4 x 3 x 2 x 1 = 40320
 
 
 
 
 
 
 
  
     
   
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