import java.math._

val twelve = new BigInteger("12")

def find(root: BigInteger, generator: BigInteger, toFind: BigInteger) =
  Stream from 1 filter (root.pow(_).mod(generator) == toFind) take 4 toList

find(new BigInteger("2"), new BigInteger("13"), twelve)
res1: List[Int] = List(6, 18, 30, 42)
// 1

find(new BigInteger("6"), new BigInteger("761"), twelve)
res2: List[Int] = List(727, 1487, 2247, 3007)
// 47

find(new BigInteger("11"), new BigInteger("1597"), twelve)
res3: List[Int] = List(9190, 25316, 41442, 57568)
// 175189