SOLUTION: if first term of n A.P.'s is 1 and their respective common differences are 1,2,3,..........,n,then prove that sum of their n terms will be n(n^2+1)/2

Question 1012721: if first term of n A.P.'s is 1 and their respective common differences are 1,2,3,..........,n,then prove that sum of their n terms will be n(n^2+1)/2
Answer by fractalier(6550) (Show Source): You can put this solution on YOUR website!
I'm looking at this, but I am not entirely clear what you mean...if the common differences are 1,2,3,...,n and the first term is one, the series looks like this to me:
1+2+4+7+11+16+22+29+37+46+...
Here n=10, so their sum should equal 10(10^2+1)/2 = 505, but it doesn't...even if n=9, the sum should be 369, and it isn't...
I am intrigued by the problem...please clarify...
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