Tuesday, August 8, 2017

sequences and series - Intuitive ways to get formula of cubic sum


Is there an intuitive way to get cubic sum? From this post: combination of quadratic and cubic series and Wikipedia: Faulhaber formula, I get 13+23++n3=n2(n+1)24

I think the cubic sum is squaring the arithmetic sum 13+23++n3=(1+2++n)2
But how to prove it? Please help me. Grazie!


Answer



Maybe this will help you visualize it:



Source.



or this one which is clearer:


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