You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named 4-[4-[4-(2,3-dichlorophenyl)piperazin-1-yl]butoxy]pyrazolo[1,5-a]pyridine is given. What is its corresponding molecular formula?
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C21H24Cl2N4O
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