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(1)+(1+2)+(1+2+3)....... it is in a A.P series.Find sumtotal upto n-th term.

 Apr 23, 2016

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 #2
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This is strictly NOT a A.P. This is called "Sequence of trianangular numbers", and can be summed up using the following formula: n[n +1]*[n + 2] / 6. So, the first 10 terms will sum up to:[10*11*12]/6=220.

 Apr 23, 2016
 #1
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I think that the sumtotal upto n is n.

edit: never mind it is wrong, I only tried when n=1,2,3 and all of them had a sumtotal of a squared number.

 Apr 23, 2016
edited by Guest  Apr 23, 2016
 #2
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+6
Best Answer

This is strictly NOT a A.P. This is called "Sequence of trianangular numbers", and can be summed up using the following formula: n[n +1]*[n + 2] / 6. So, the first 10 terms will sum up to:[10*11*12]/6=220.

Guest Apr 23, 2016
 #3
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 I think you don't know that it is a formula of A.P

AaratrikRoy  Apr 23, 2016

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