Expected number of subnodes of a randomly selected node in a tree.

excpectedNumOfSubnodes.scala

def propab(d: Int, n: Int, b: Int): Double = {
  Math.pow(b,d-1)/Math.pow(b,n)
}

def expected(n:Int, bf: Int): Double = {
  (1 to n).foldLeft(0.0)( (a:Double,b:Int) => a + (b*propab(b,n,bf)) )
}