You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[3-(2,4-dimethylphenyl)-1,2,4-oxadiazol-5-yl]-7-piperidin-4-yl-2,3,3a,4-tetrahydro-1H-pyrazolo[1,5-a]pyrimidin-5-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H26N6O2
assistant