[tex]\displaystyle \\
1 + 3 +5+ \cdots + 2011 = ? \\
\text{Calculam numarul de termeni: } \\ \\
n = \frac{2011 - 1}{2}+1 = \frac{2010}{2}+1 = 1005+1 = \boxed{1006 ~termeni} \\ \\ \\
S = 1 + 3 +5+ \cdots + 2011 = \\ \\ = \frac{1006(2011+1)}{2}= \frac{1006\times2012}{2}= 1006\times 1006 = \boxed{\boxed{1006^2}}[/tex]
