Algebra
# Arithmetic Progressions

Evaluate

$1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19.$

$\begin{array} { l l l } 2 & = 2 & = 1 \times 2 \\ 2 + 4 & = 6 & = 2 \times 3 \\ 2 + 4 + 6 & = 12 & = 3 \times 4 \\ \vdots & \vdots & \vdots \\ \end{array}$

According to the above pattern, what is

$2 + 4 + 6 + \ldots + 30 ?$