Math help for oblivion

Hello all. I’m rusty at math. So, I need help changing this math equation for an oblivion mod, oblivion xp updated.

XP (x) = multXPNeeded * (QuadraticAmp * atan(QuadraticSlope * x^2 / 250) + Linear * x + Base)

I’m looking for a ^ constant growth curve and no leveling off, but be able to control how quickly XP goes up. How do change the math do that?