hp50g calculator equivalent on android (no emulators)

[Eddie W. Shore]

A good scientific Android app is RPNPlus: trig, hyperbolic functions, exponential, linear regression, Gaussian distribution and density, present value function (rate ENTER n PV: present value annuity factor)

I also like go25C (I know it's an emulator, but the keys are nice and big).

I will also throw in a recommendation for Maxima and xCas.

If you like writing your equations with a finger or stylus, check out MyScript Calculator.