It is formed as-
take a paper and draw angle of 90 degrees on it.
fold paper on both arms of angle to form a crease.
suppose the basea arm as i unit.
take a compass and draw a arch cutting perpendicular.
join ending point of base arm and point where it cut the perpendicular and make a crease.
then again make a perpendicular on hypo. of that angle.
do it further till oyu get the number to which you want to represent.