You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
tert-butyl 4-[3-(5-ethyl-1,2,4-oxadiazol-3-yl)-5-oxo-4H-pyrazolo[1,5-a]pyrimidin-7-yl]piperidine-1-carboxylate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H26N6O4
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