Ray Bellis wrote:
> stbenge wrote:
>> Hi everyone,
>>
>> Today I figured out a couple of mathematical expressions to find the
>> number of bricks for any given 2d or 3d pyramid. I had previously
>> figured out the 2d version, but the equation was a bloated
>> monstrosity. The new one is much simpler!
> 
> http://pirate.shu.edu/~wachsmut/ira/infinity/answers/sm_sq_cb.html
> 
> 2D pyramid = 1 + 2 + 3 + .. + n
>            = n * (n + 1) / 2
> 
> 3D pyramid = 1 + 2^2 + 3^2 + .. + n^2
>            = n * (n + 1) * (2n + 1) / 6

Yeah well, like I said, it was fun to come up with this independently. I 
wonder if anyone else has used a similar geometric approach?

Sam

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