All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Just Math
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)

Comments: ( Back to comment list | You must be logged in to post comments.)
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
Please log in:
Remember me:
Sign up! | Forgot password

Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (4)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Copyright © 2002 - 2018 by Animus Pactum Consulting. All rights reserved. Privacy Information