title: Find the most points enclosed in a fixed size circle
body: <p>This came up when a friend talked about a programming competition, and we wondered what the best approach was:</p>
  
  <p>Given a list of points, find the centre of a circle of predetermined size that covers the most points.  If there are several such circles, its only important to find one of them.</p>
  
  <p>Example input: 1000 points, in a 500x500 space, and a circle of 60 diameter.</p>