When I save and reopen an excel workbook which include formulas inside (such as =STDEV(B2:B251)*SQRT(252)) the formulas will be gone and only the value remains. You must save the file in an Excel format, e.g. xlsx. If you save the file e.g. as csv the formulas are gone because that is a text file, not an Excel spreadsheet file. Andreas. More @Wikipedia
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