The 3x+1 Iterator (The Collatz Problem, which you'll soon see gets quite interesting)

main.py

import matplotlib at plt
import numpy as npy

def f(arr, n, goal):
    if n==goal: return arr
    if arr[-1]%2==0: return f(arr+[(0.5*float(arr[-1]))],n+1,goal)
    else: return f(arr+[3.0*float(arr[-1])+1], n+1, goal)
    
N = 150
x,y = range(N), f([14],1,N)
x2,y2 = range(N), f([14],1,N)

plt.plot(x2,y2)
plt.figure()
plt.plot(x,y)