""" Get the number of 2 that appear 
    from 0 to a number n. (22 counts by 2)
    
    For example: n=60
    Output:  2,12,20,21,22,23,24,...,32,42,52

    For every decimal, there's one 2 except 20's
    
    100 = 10 (decimals) + 10 (twenties)
    1000 = 100 (decimals) +  

"""
