Question Number 27688 by NECx last updated on 12/Jan/18
$${Write}\:{the}\:{series},{indicating}\:{the} \\ $$$$\mathrm{5}{th}\:{term},{the}\:\mathrm{5}{th}\:{partial}\:{sum} \\ $$$$ \\ $$$$\mathrm{0}+\mathrm{1}+\mathrm{3}+...+\left(\frac{{n}^{\mathrm{2}} +{n}}{\mathrm{2}}\right)+... \\ $$