I tried out the github script and it wokrs fine. hope it keeps working.

I already found the gform_calculation_formula filters in the GF manual but then I have to write the script over and over again for each form, field I want to use, am I correct?

thank you, the githib script does work on latest wp install although its 3 years old. Maybe good for others to knwo.
The price of $99 for the calculation plugin is a little to much for just this only exponent calculation, but I keep that one in mind.