It’s seen that, the initial term is \[\left( a \right)\text{ }=\text{ }1\]
What’s more, typical ratio \[\left( r \right)\text{ }=\text{ }2/\text{ }1\text{ }=\text{ }2\]
We realize that, the overall term is
\[{{t}_{n}}~=\text{ }a{{r}^{n\text{ }\text{ }1}}\]
So,
\[{{t}_{n}}~=\text{ }\left( 1 \right){{\left( 2 \right)}^{n\text{ }\text{ }1}}~=\text{ }{{2}^{n\text{ }\text{ }1}}\]