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So many quintuplets... (Posted on 2011-03-17) Difficulty: 3 of 5
Determine the total number of quintuplets (A,B,C,D,E) of positive integers such that A<=B<=C<=D<=E<=N. Both analytic and software solution for N=1, 2, ...9,10,...N required.

See The Solution Submitted by Ady TZIDON    
Rating: 4.0000 (3 votes)

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re: solution + spoiler Comment 3 of 3 |
(In reply to solution by Charlie)

Kudos for excellent presentation and solution.

I will refer to it when posting the "official" solution.

I will only add a recursive formula for f(n), to facilitate the
numerical evaluation":

f(1)=1;   f(n)=f(n-1)*(f+4)/(n-1)


hence  f(2)=1*6/1=6  f(3)=6*7/2=21 etc matching your results.

 

 


  Posted by Ady TZIDON on 2011-03-17 18:34:07
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