How to use in-sentence of “factorial”:
+ This code calculate factorial of a positive integer, using recursion.
+ The problem with this is that for N cities you have factorial possibilities.
+ The factorial has special application in defining the number of permutations in a set which does not include repetitions.
+ The factorial function is a good example of recursion.
+ Double factorial is a method of calculating how many times a number is repeated in a geometric equation.
+ This function computes the factorial of a natural number.
+ Similarly the rising factorial is a multiplication of progessively larger terms starting with n where there are k number of terms.