def hailstone(n):
    seq = [n]
    while n>1:
        n = 3*n + 1 if n & 1 else n//2
        seq.append(n)
    return seq

if __name__ == '__main__':
    h = hailstone(27)
    assert len(h)==112 and h[:4]==[27, 82, 41, 124] and h[-4:]==[8, 4, 2, 1]
    print("Maximum length %i was found for hailstone(%i) for numbers <100,000" %
          max((len(hailstone(i)), i) for i in range(1,100000)))