## Geometry: Common Core (15th Edition)

Alternate between adding 1 and 3 to the prior term to get the next term. $\underset{+1}{\underset\Rightarrow{1}}, \underset{+3}{\underset\Rightarrow{2}},\underset{+1}{\underset\Rightarrow{5}}, \underset{+3}{\underset\Rightarrow{6}},\underset{+1}{\underset\Rightarrow{9}}, \underset{+3}{\underset\Rightarrow{10}}, 13$, . . .