You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named (1E,3E,6E,7Z)-6-ethylidene-1-(3,4,5-trimethoxyphenyl)nona-1,3,7-trien-5-one by IUPAC nomenclature, provide its molecular formula.
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C20H24O4
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