Megan's Granny Rectangle
By: Megan Mills from megan.cc
"I wanted something longer than a granny square--but only just. I also wanted it to have as many 3-tr sets as possible originating in a shared center, without any center having more than 4 sets in it. After experimenting I made a bonus discovery: this is extendable. You don't have to calculate in advance how many chains you need to start."