Bobby Fischer dead at 64

Re:Bobby Fischer dead at 64 by eru on Sunday January 20, 2008 @07:05AM (#101199)

This thread is pedantic.

By thy way:

  sum(i=1..n) i*i = n/6 + n^2/2 + n^3/3

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Re:Bobby Fischer dead at 64 by jgrahamc on Sunday January 20, 2008 @09:42AM (#101228)

Proof?

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Re:Bobby Fischer dead at 64 by hhm on Sunday January 20, 2008 @10:04AM (#101237)

This proof helps: http://pirate.shu.edu/~wachsmut/ira/infinity/answers/sm_sq_c...

From that: sum bla= n(n+1)(2n+1)/6, then you go distribute

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Re:Bobby Fischer dead at 64 by eru on Monday January 21, 2008 @03:29AM (#101488)

Nice. How did I get the result in the first place?

I know that this sum can be expressed as a cubic polynomial. So I just evaluated the sum at four data-points (n=0,1,2,3) and used those to determine the four coefficents by solving a linear equation system.

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Re:Bobby Fischer dead at 64 by jgrahamc on Monday January 21, 2008 @08:11AM (#101534)

Turns out that drawing a picture really helps: http://news.ycombinator.com/item?id=101532

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Re:Bobby Fischer dead at 64 by eru on Monday January 21, 2008 @06:12PM (#101875)

You can usually come up with a clever picture only after you understood the problem - not before.

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