`` How did the '' '' _ + _ + _ = 30 using 1 , 3 , 5 , 7 , 9 , 11 , 13 and 15 '' '' riddle become so popular ? ''
What is the function for the serie 15 , 0 , 1 , 14 , 3 , 12 , 13 , 2 , 7 , 8 , 9 , 6 , 11 , 4 , 5 , 10 ?