''' Purpose: practice function chresthomathics``
'''

import math

def summation( n ) :
    ''' For integer parameter n, returns the sum of 1 + ... + n.
    '''

    ...

    return result

def sample( d ) :
    ''' Returns an integer estimate of the age of a fossil with a carbon-12 to
        carbon-14 ratio of d
    '''

    pass

def has_vowel( w ) :
    ''' Returns True or False depending whether a lower-case vowel is part
        of string d
    '''

    pass