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Compute the sum

2123+2234+2345+...

 May 29, 2017
 #1
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0

Since the denominators in your sequence follow a pattern of: 6, 24, 60, 120, 210, 336...etc. and continue at this pattern:n^3+3n^2+2n......to infinity, the reciprocal of all terms converging to 1/4. Therefore, your sequence will converge to: 2[1/4] =1/2.

 May 29, 2017
 #2
avatar+118703 
+1

Please can we explain your logic better guest ?

 May 30, 2017
 #3
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See here: http://www.wolframalpha.com/input/?i=%E2%88%91+1%2F%5Bn%5E3%2B3n%5E2%2B2n%5D,+for+n%3D1+to+1000000

 May 30, 2017
 #4
avatar+118703 
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mmm ok...

thanks for responding :)

Melody  May 30, 2017
 #5
avatar+9675 
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a1=2123=13a1+a2=2123+2234=512a1+a2+a3=2123+2234+2345=920a1+a2+a3+a4=2123+2234+2345+2456=715a1+a2+...+a5=715+2567=1021a1+a2+...+a6=1021+2678=2756

It seems like it will not exceed 1/2.

So the answer is 1/2

 May 30, 2017

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