def collatz_sequence(x):  
    num_seq = [x]  
    if x < 1:  
       return []  
    while x > 1:  
       if x % 2 == 0:  
         x = x / 2  
       else:  
         x = 3 * x + 1  
    # Added line  
       num_seq.append(x)      
    return num_seq  
  
print(collatz_sequence(12))  
  
print(collatz_sequence(19))