Is someone so nice and explain this verbally? I dont really get what '...j=iJ' is supposed to mean
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Sum of the sum of j, with j going from i to n, with i going from 1 to n
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Pyramid number represents the number of stacked spheres in a pyramid. It's a 3D version of triangular numberspic.twitter.com/WZ8324vBGH
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Here's another way to look at it :) . The left part is just the sum of the columns of a matrix, starting in the main diagonal, where each element is equal to index of the column.pic.twitter.com/DtEv4Q1e08
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Thanks, Fermat. A proof we needed/deserved.
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Interesting, using this visual proof, if you telescope the squares 4^2-3^2+2^2-1^2, you get 10, the same as 4 + 3 + 2 + 1
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Pa que aprende un poco mas sobre las series de Taylor y de Mclaurin
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Neat proof. But use induction instead of hoping for a clever geometric construction:pic.twitter.com/VoCYBAkYLW
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Cool thanks
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