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A prime factorization problem (Posted on 2006-08-07) Difficulty: 4 of 5
Define polynomials Fn(x) such that for all nonnegative integers n:

F0(x)=1, Fn+1(0)=0 and

F'n+1(x) = (n+1)Fn(x+1)

Find the prime factorization of F300(7).

  Submitted by K Sengupta    
Rating: 4.0000 (2 votes)
Solution: (Hide)
An examination of the low order cases lead one to conjecture that:
F_n(x) = x*(x+n)^(n-1)

Clearly, this satisfies F_0(x) = 1; F_n(0) = 0 for n>=1

Now; F’_n+1(x)
= (x+n+1)^n + n*x*(x+n+1)^(n-1)
= (n+1)(x+1)(x+n+1)^(n-1)
= (n+1)*F_n(x+1)

Hence, F_n(x) = x*(x+n)^(n-1), as conjectured earlier.

Consequently, F_300(7) = 7*(307^299).

Comments: ( You must be logged in to post comments.)
  Subject Author Date
SolutionSpoilerRichard2006-08-07 13:45:55
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