A theory pioneered by R. Khan that predicts the number of arrangements (A) there are for a number, n, of cross-over points in the loop. It turns out, after much study, A = 2n.
In a loop with 2 crossover points, there are 4 different arrangements. I learned this using LOOP THEORY!
ayon kay MathScribe ika-24 ng Pebrero, 2009