You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(E)-3-(4-ethoxyphenyl)-N-[(8-methylimidazo[1,2-a]pyridin-2-yl)methyl]prop-2-enamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H21N3O2
assistant