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Google recently added a cool calulator feature.
Simply enter a math formula like "5 * 5" into Google and it will return a results page with the answer. 

 Asking Google: "The answer to life, the universe and everything" returns the calculator and the answer 42, based on the calculation by Deep Thought, the super computer in the Douglas Adam's classic "Life the Universe and Everything".
Google also links to a Wikipedia entry that explains how 6 * 9 = 42 (hint: not base 10) and how code written in C using macros also correctly multiplies 6*9=42.  I also work in building 42 which makes it that much more special :)

Another cool feature I discovered is that Google does factorials. Entering 4! and you'll see 4*3*2*1 (x * x-1) or 24.  This reminded me of French mathematician Blaise Pascal who's Pascal triangle solves probabability questions. For example, look at the triangle below:

1			1	1
	
2		    1       2       1

3		1	3	3	1

4	    1	    4	    6	    4       1

5	1	5	10	10	5	1

6   1	    6      15        20      15      6       1

1	2
    3

4	6
   10

The numbers horizontally represents the possibilities of elements being picked.  Let's use the 4th row and letters A, B, C, D as examples. The fourth row represents the numbers 1, 4, 6, 4, 1 which represent the probability of choosing 0, 1, 2, 3, and 4 of the letters. Let's look at each of these:

0 - There is only one option for picking none of the letters.
1 - Since there are four unique letters, there are four unique possibilities. 
2 - There are six ways of picking exactly two letters: AB, AC, AD, BC, BD, CD.
3 - There are four ways of picking three out of the four elements, simply choose which letter you are not going to pick.
4 - There is only one way to select all of the letters.

Whew, with that explained, we can look at the mathematical formula for this:
N!/(R!(N!-R!)) where N represents the number of elements and R represents the number of matches.

Using our example above, where N is 4 and we'll set 2 as the number of matches, we get:

 4!/(2!(4-2)!).  Google correctly answers this as 6, matching the value in Pascal's triangle. 

If you didn't have Google, you can represent Pascal's formula in C# with the code below: 

	
class f
{
	//Factorial
	private static long fac(long x)
	{
		for(long i=x-1;i>0;i--)
		{
			x *= i;			
		}
		return x;
	
	}

	public static long Pascal(long n, long r)
	{
		
		return fac(n)/(fac(r) * fac(n-r));
	
	}
}

Another interesting mathematical pattern in Pascal's triangle is the Fibonacci sequence on the triangle diagonals.

Cool stuff, now do we call Google's calculator a web service?