I have been finding formulae at various math tutorial websites and pasting them into a Calc file, typically by first washing the text string through Notepad and/or LibreOffice Writer.
Surely there is no need to "wash" anything if you paste as Unformatted text?
My goal, in part, is to model a formula of interest within Calc, e.g., a^2 = b^2 + c^2 - 2bc Cos A; this is one way that allows me to learn how to manipulate Calc's functions. So, I used Writer's superscript button and then pasting the formula into my Calc file, as a text string, of course.
A perfect task for tables in a text (Writer) document, not a spreadsheet. Time taken to learn the basics of tables in a text document: three minutes? Oh, and even easier: if you copy the range of cells you currently have in a spreadsheet and paste that into a text document, choosing possibly HTML or "Formatted text" in the Paste Special dialogue, a table will be created for you.
Note that text tables are worth knowing about: they are frequently useful for formatting material in a text document that doesn't immediately appear to be tabular.
I trust this helps.
Brian Barker