Squared triangular number

57 Views Asked by At

Say I have n=5 I would like to perform the following equation:

5^2 + 4^2 + 3^2 + 2^2 + 1^2 = 55

I know that a triangular number can be worked out with the following equation:

(n(n+1)/2)

However it is at this point where I've not been able to work out the required adjustments to suite this use case.

What would be the correct equation?

1

There are 1 best solutions below

0
On BEST ANSWER

$$\sum_{k=1}^n k^2 = \frac{1}{6}n(n+1)(2n+1)$$ with n=5 :$$\frac{1}{6}*5*6*11=55$$ it is sometimes called number for quadratic pyramid. trula