This is more of a mathematics question rather than programming.

Well, I would like to ask id you know what is the interpolator described in Material design:

It looks to be an AccelerateDecelerateInterpolator but the deceleration effect decays slower.

My best hatch is :

public class MaterialInterpolator implements Interpolator {

    @Override
    public float getInterpolation(float input) {
        if(input<1./3f)
            return new AccelerateInterpolator().getInterpolation(input);
        else
            return new DecelerateInterpolator().getInterpolation(input);
    }

}

Which creates a gap between the values:

Time / Value
0.3,0.09
0.317,0.100489
0.333,0.110889  <-- gap
0.35,0.57750005
0.367,0.599311
0.383,0.61931103
0.4,0.64

Source: http://www.google.com/design/spec/patterns/imagery-treatment.html