the numerical order of the numbers in it. This property is not true of the Calkin–Wilf tree. Notes References . . . EWD 570: An exercise for Dr.R.M.Burstall, pp. 215–216, and EWD 578: More about the function "fusc" (A sequel to EWD570), pp. 230–232, reprints of notes originally written in 1976. . . External links Integer sequences Trees (data structures)