Monday, February 8, 2016

prime factorization - Power of 2 & 5 in product of consecutive numbers




Is there any way to calculate the powers of 2 and 5 in a product of consecutive n numbers, if given l and r.



i.e Suppose x=l×(l+1)×(l+2)×......×(r1)×r, Then if x=2p1.3p2.5p3.7p4...., So I am interested a direct way of calculating p1 and p3 with just l and r



I am just curious about it. I just want 2 & 5, but if there is a general solution for any prime number, It would be great if you mention that.


Answer



Let, us define the product of first n integers by n!.



Now,highest power of prime p contained in n! is given by-




phighest power=np1+np2+np3+...+npn

where pnn and x is the greatest integer function.



For more information see this-De Polignac's Formula.


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