Well we don't have the choices, maybe they're coming.
We want r(1)=2, r(2)=5, r(3)=8, ...
We can write that
That's equivalent to
Hopefully those are the two expressions among the choices. There are many equivalent expressions but these are the most likely.
We want r(1)=2, r(2)=5, r(3)=8, ...
We can write that
That's equivalent to
Hopefully those are the two expressions among the choices. There are many equivalent expressions but these are the most likely.