## Writhe

Also called the Twist Number. The sum of crossings of a Link ,

where defined to be if the overpass slants from top left to bottom right or bottom left to top right and is the set of crossings of an oriented Link. If a Knot is Amphichiral, then (Thistlethwaite). Letting Lk be the Linking Number of the two components of a ribbon, Tw be the Twist, and Wr be the writhe, then