> Arrange the numbers 1,1,2,2,3,3,4,4.....15,15,16,16 in such a way that > there is one number between the ones, two numbers between the twos and > so on up to 16 so that there are 16 numbers between the 16s. See "Langford's Problem" <http://www.lclark.edu/~miller/langford.html>