You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Translate the chemical IUPAC name 2-[(4-phenylazepan-1-yl)methyl]-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine into its molecular formula.
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C20H28N4
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