diff -r 7a5a29a32568 -r ab77f6006f1f progs/knight2.scala
--- a/progs/knight2.scala	Thu Nov 03 01:05:20 2016 +0000
+++ b/progs/knight2.scala	Sat Nov 05 17:11:47 2016 +0000
@@ -26,7 +26,7 @@
 
 // non-circle tours
 def tour(n: Int)(steps: List[Pos]): List[List[Pos]] = {
-  if (steps.length ==  n * n) List(steps)
+  if (steps.length ==  n * n && moves(n)(steps.head).contains(steps.last)) List(steps)
   else 
     (for (x <- moves(n)(steps.head).par; if (!steps.contains(x))) yield tour(n)(x :: steps)).toList.flatten
 }
@@ -35,4 +35,5 @@
 val n = 6
 println(s"number simple tours: n = $n")
 
-println((for (i <- 0 until n; j <- 0 until n) yield tour(n)(List((i, j)))).flatten.distinct.size) 
+println(tour(n)(List((1,1))).distinct.size)
+//println((for (i <- 0 until n; j <- 0 until n) yield tour(n)(List((i, j)))).flatten.distinct.size)