27020 (Gheorghe Szöllösy)
Să se calculeze suma ∑ k = 0 [ n 2 ] i {\displaystyle \sum _{k=0}^{\left[{\frac {n}{2}}\right]}i}
![{\displaystyle \sum _{k=0}^{\left[{\frac {n}{2}}\right]}i}](https://wikimedia.org/api/rest_v1/media/math/render/svg/1a46f21781546c89b7314a5cb3cec005049720fa)