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According to the Wikipedia article [1], it equals -1/12 (R), except the R is written a rather fancy script.

Now, I'm no mathematician, but I'm betting that (R) is important, and affects the true value of the -1/12, and probably should not be omitted.

[1] http://en.wikipedia.org/wiki/Ramanujan_summation

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There's only one way to add a finite list of numbers, but several ways to "add" infinite lists. Ramanujan summation is just one way. There are also other ways to define "addition" on infinite lists: Abel, Borel, Cesaro, Euler, etc. summation.

They're different from each other because they disagree on certain infinite sums, but they're still considered "summations" because, for finite lists, they give the same answer as normal addition.

So the title should instead read "The sum of all positive numbers up to infinity (for a certain definition of 'sum') is -1/12".

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