Posted by **Anonymous** on Monday, February 4, 2008 at 7:18pm.

Is there a mathematical formula to calculate this easily?

1 x 2 x 3 x 4 x 5...50

I know it's not an arithmetic/geometric series because that means 1 + 2 + 3 + 4 + 5...50

- Math -
**Count Iblis**, Monday, February 4, 2008 at 7:37pm
There exists a method that allows you to compute this very accurately (and very easily). The formula in this case is:

n! = n^n exp(-n) sqrt(2 pi n)

exp[1/(12 n) - 1/(360 n^3)

+ 1/(1260 n^5) -1/(1680 n^7)+... ]

Here n! = 1 x 2 x 3 x...x n

So, let's test this formula for n = 50. The exact answer you get by multiplying all the factors is:

50! = 3.04140932017..... x 10^(64)

If you evaluate n^n exp(-n) sqrt(2 pi n)

(this is known as Stirling's approximation) for n = 50 you get:

3.03634459394...x 10^64.

The asymptotic series in the exponential is:

1/(12 n) - 1/(360 n^3)

+ 1/(1260 n^5) -1/(1680 n^7)+...

for n = 50 this is

1.66664444699...x10^(-3)

The exponential of this number is

1.00166803407...

3.03634459394...x 10^64 times 1.00166803407... equals 50! to 12 significant figures!

- Math -
**desteny**, Saturday, February 9, 2008 at 12:12am
1x2=2x3=6x4=24x5=120

## Answer This Question

## Related Questions

- algebra - Can someone please help me with this problem? Thanks! Evaluate the ...
- math studies - An arithmetic series has a first term of -4 and a common ...
- math - is there a formula for an INFINITE ARITHMETIC series/sequence? i know its...
- Math (Geometric Progression) - 5 distinct positive reals form an arithmetic ...
- Math - 5 distinct positive reals form an arithmetic progression. The 1st, 2nd ...
- Math - Using the index of a series as the domain and the value of the series as ...
- Math Help!!! - determine whether each sequence is arithmetic or geometric. find ...
- math - The sum of the 1st nine terms of an arithmetic series is 216. The 1st,3rd...
- Math - Determine whether this sequence is arithmetic or geometric. Find the next...
- Math - Consider the following series: 1,2,3,4,5,10,20,40....which starts as an ...

More Related Questions