In my 10th class school material, it is given that Aryabhatta discovered the following formulas:
$\sum n=\dfrac{n(n+1)}{2}$
$\sum n^2=\dfrac{n(n+1)(2n+1)}{6}$
$\sum n^3=\dfrac{n^2(n+1)^2}{4}$
Is he the first person to discover these formula? If this is true, then who discovered the formula for the generalization $\sum n^k$ ?