[R] Fleiss Control Size Formula

[tom4201]

I am trying to compute the smallest control group size using Fleiss
formula. Assuming that my population is 5,000, the smallest expected
lift (smallest detectable change) is 5%, and the highest likely rate
in the control group is 50%, what is the minimum control group size
assuming a 95% confidence interval and power of 80%? I am more
interested in the adjusted Fleiss formula to compute the control group
size.

Thanks,