Lucky numbers

UnLuckyNumbers.scala

//Lucky numbers challenge
//http://codegolf.stackexchange.com/questions/94695/unlucky-numbers
case class LuckyNumbers(val n: Double, seq: Seq[Double] )
case class Test(val m: Int, val n: Int, val expected: Double)

object LuckyNumbers{
	def natural_numbers(max: Double) = {
		def next(n: Double, seq: Seq[Double]): Seq[Double] = if(n >= max) seq ++ Seq(n) else next(n+1, seq ++ Seq(n) )
		next(1, Seq())  
	}
	//lucky numbers
	def L(n: Int, seq: Seq[Double]) = {
		require( n <= 100 , "Constraint: n <= 100")
		def lucky(_n: Int, _seq: Seq[Double]) = _seq.grouped(_n).toList.map{_.take(_n-1)}.flatten
		def filter(_n: Int, _seq: Seq[Double]): Seq[Double] ={
			if( _n == n ) 
				lucky(_n, _seq)
			else
				filter(_n+1, lucky(_n,_seq))
		}
		if(n <= 1) seq else filter(2,seq)	
	}
	//unlucky numbers
	def U(n: Int, seq: Seq[Double]): Seq[Double] = {
		L(n, seq).diff( L(n+1, seq) )
	}

}

object LuckyNumbersChallenge{
	
	def main(args: Array[String]){
		val max: Double = 1e3//should support up to 1e6 , using 1e3 to increase speed	
		val nat = LuckyNumbers.natural_numbers(100)
		Seq(
			Test(10,1,20),
			Test(5,2,29)
			
		).map{
			case Test(m,n,expected) => assert(LuckyNumbers.U(n, nat)(m-1) == expected, Test(m,n,expected))
		}
	}
}