Are they related?

Algebra Level 2

\[ \begin{array} { l l l l l l l l l l } &1 & + &2 & + &3 & + & \ldots & + & n & = & 300 \\ &1^3 & + &2^3 & + &3^3 & + & \ldots & + & n^3 & = & \ ? \\ \end{array} \]