User blog comment:Deedlit11/Bignum Bakeoff appetizer/@comment-10281778-20141123040319

Modified Goodstein Function in Python 3. i = 9 ** 9 ** 9 b = 2

B = lambda y,x=0:y and y % b * (b*b)**B(x) + B(y//b,x+1)

while i:   i = B(i)-1 b *= b print(b) 85 characters.