java.utils.Random possible seeds from nextInt(int)

I've been having the problem that I need to efficiently generate Seeds which to use for getting a specific Random Number output in Java. As I've seen in several Threads(Most importantly this one) Java's RNG from java.utils.Random is easily reversible. The problem I am now facing is that I do not know how to find all possible seeds for a given result from Random.nextInt(int n) which provides a 31 bit Random Number mod n. As previously stated I also have the additional requirements of needing a "fast" algorithm, that also needs to be able to take multiple requirements from different calls to the method. To narrow down the case, I need this to work for n = 27 and n = 23.