the most famous Ramanujan sum 1+2+3+...=-1/12
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Numberphile v. Math: the truth about 1+2+3+...=-1/12
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a spectacular solution to the Basel problem (sum of 1/n^2 via a complex integral)
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This Result Keeps Me Up At Night
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A Brilliant Limit
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Making Sense of Ramanujan's Infinite Sum for General Audience.
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The Most Beautiful Equation in Math
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so you want a VERY HARD math question?!
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