No, but you can convert a RNG that emits 4 equally likely values into an RNG that emits 3 equally likely values. Just - anytime the RNG returns 4, try again.
Here's a fun puzzle / annoying interview question: You have a biased coin. You can flip it as often as you want, but heads and tails are not equally likely. Without figuring out the bias of the coin, how do you produce purely random bits?
