The condensed formula of propane is
The formula for propane is C3H8. But as you can observe this way of representing a compound gives us no information about its structure and the distribution of hydrogen with each carbon atom. Let's look at the structure of propane now.
In the condensed representation of compounds, we don't show the bonds connecting the atoms. It is just a sequence of the type and number of atoms in the compound. Therefore, the condensed form of propane is
CH3CH2CH3