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Not too much (Posted on 2015-02-20) Difficulty: 2 of 5
What is the sum of the reciprocals of all the nonzero
triangular numbers?

No Solution Yet Submitted by Ady TZIDON    
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re(2): Is this valid? no ! - partial spoiler | Comment 6 of 8 |
(In reply to re: Is this valid? no ! - partial spoiler by Ady TZIDON)

I was surprised the answer was 2 myself since it's the same as the 2^-n series, but I looked it up.

However they switch term-wise with the triangular numbers reciprocals first smaller then larger than the geometric.

I know that re-grouping terms doesn't always work as
(1+-1)+(1+-1)+...≠1+(-1+1)+(-1+1)...
but since I got the correct answer I want to know if I was somehow "cheating."



  Posted by Jer on 2015-02-20 21:19:34

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