I know that the highest power of a prime which divides n! is given by
[np]+[np2]+[np3]...
Where [x] is the greatest integer function.
For nPr, which equals n!(n−r)!, I can find the highest power of p dividing n! and (n−r)!, and then subtract the two to get the highest power of p dividing nPr.
Now is there a better method to do this, where we don't need to find the highest power of p dividing (n−r)!? Can we directly find the power of p dividing the product of r consecutive integers?
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