proposed by | Toby Walsh tw@cs.york.ac.uk |
The problem generalizes to the L(k,n) problem, which is to arrange k sets of numbers 1 to n, so that each appearance of the number m is m numbers on from the last. For example, the L(3,9) problem is to arrange 3 sets of the numbers 1 to 9 so that the first two 1's and the second two 1's appear one number apart, the first two 2's and the second two 2's appear two numbers apart, etc.
A graphical representation of L(2,4), with black=1, red=2, blue=3 and yellow=4 is given below.