Gary Thomas wrote:
> Except for calculating binomial coefficients for probability calculations or
> closely related things. I can't think of any reason to calculate large
> factorials. In the case of binomial coefficients it is better to cancel out
> some of the factors and avoid calculating the huge factorials. If the
> numbers are large, the use of approximations is almost certainly a better
> approach
>   
A rule of thumb I was taught in the days when compute power was 
expensive was that any factorial over 10! should be done using 
Stirling's approximation. I think that's a reasonable strategy even today.

-- 
M. Edward (Ed) Borasky, FBG, AB, PTA, PGS, MS, MNLP, NST, ACMC(P)
http://borasky-research.net/

If God had meant for carrots to be eaten cooked, He would have given rabbits fire.