Square Root Series

>>> #http://math.stackexchange.com/questions/1140503/nested-radicals-of-1000-square-roots
>>> x = 0.5 * (9.0 - 17**0.5)
>>> a0 = x ** 0.5
>>> a1 = (x+a0)**0.5
>>> x, a0, a1
(2.4384471871911697, 1.5615528128088303, 2.0)