The Crab curve is not exactly a Koch curve, but that's still a fractal and it's built rather similarly. This time, we grow square triangle on the side of the figure: the angle is 45 degrees, and the length is divided by [!java|scala]Math.sqrt(2)[/!][!python]math.sqrt(2)[/!][!c]sqrt(2);[/!] at each step.
Check the figures produced by the first steps of recursion to understand the pattern.
This curve, also called the Lévy C curve was invented in 1938 by the French mathematician Paul Lévy. As usual, the wikipedia page is very instructive, and the page provide very good additions: http://www.mathcurve.com/fractals/c/c.shtml.