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A comment on Does 1+2+3+... Really Equal -1/12?.

Re:Does 1+2+3+... Really Equal -1/12? by olsgaard on Saturday July 16, 2016 @08:39AM (#12106156)
In the numberfile video he doesn't explain the way he calculates 2・S_2. He says he shift it, but doesn't explain why that is valid.

    Shifted version:
         1-2+3-4+5-6 ...
           1-2+3-4+5 ...
    sum: 1-1+1-1+1-1 ...
    
    Multiplied version:
         2-4+6-8+10-12 ...
The multiplied version shifts between +(2n) and -(2n). Following the logic that S_1 = 0.5, because that is the average between 0 and 1, I would argue that the multiplied version of S2 should equal 0, as that is the average between a postitive constant and its negative (but the variance is going to be infinite. Doesn't that have a say?).

What if we triple shift?

    Triple shifted version:
         1-2+3-4+5-6+7-8+9 ...
               1-2+3-4+5-6 ...
    sum:     2-3+3-3+3-3+3 ...
Look! now 2・S2 is equal to 2!
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Re:Does 1+2+3+... Really Equal -1/12? by diogofranco on Saturday July 16, 2016 @08:55AM (#12106188)
I don't think your math adds up.

Your triple shifted version would be between -1 or 2 depending on the cut right? So, still 1/2.

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Re:Does 1+2+3+... Really Equal -1/12? by olsgaard on Saturday July 16, 2016 @04:36PM (#12107790)
Yeah, that was a brainfart on my end.

What about the multiplied version? That is how I would intuitively understand 2S_2, and I still don't accept that shifting is the same.

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