// Second Version of Ramanujan's Taxi
  def ramtaxi_O3(n: Long) = {
    for (a <- 1L to n) {
      val a3 = a * a * a
      if (a3 <= n)
        for (b <- a to n) {
        val b3 = b * b * b
          if (b3 <= n)
            for (c <- a + 1 to n) {
            val c3 = c * c * c
              if (c3 <= n) {
                val d = Math.pow(a3 + b3 - c3, 1.0 / 3.0).toLong
                if (d != a && d != b) {
                  val d3 = d * d * d
                  if (d3 <= n && a3 + b3 == c3 + d3)
                    println(a3 + b3 + " = " + a + "^3 + " + b
                      + "^3 = " + c + "^3 + " + d + "^3")
                }
              }
            }
        }
    }
  }