Wolfram Demonstrations Projecthttp://demonstrations.wolfram.com/An Open Resource of Interactive Mathematica VisualizationsCopyright 2009 Wolfram Demonstrations Project & ContributorsGeneralized Ulam Sets in the Planehttp://demonstrations.wolfram.com/GeneralizedUlamSetsInThePlane/]]>http://demonstrations.wolfram.com/GeneralizedUlamSetsInThePlane/