In the US facts are not copyrightable, so in general math is not copyrightable.
You can copyright creative expressions that use math formulas, but only that expression itself would be covered. E.g. a paper presenting a proof of a theorem would be copyrightable, but all of the facts expressed by the formulas would not be copyrightable.
Or to put a concrete point on it, Photoshop's content aware fill is ("merely") the implementation of a particular SIGGRAPH paper. The math itself isn't copyrightable, but Adobe is going to come after you if you stick their .dll files on GitHub, and probably win.
You can copyright creative expressions that use math formulas, but only that expression itself would be covered. E.g. a paper presenting a proof of a theorem would be copyrightable, but all of the facts expressed by the formulas would not be copyrightable.