Checks if credit card number fits the visa electron format.

def is_visa_electron(n):
    """Checks if credit card number fits the visa electron format."""
    n, length = str(n), len(str(n))
    form = ['026', '508', '844', '913', '917']

    if length == 16:
        if n[0] == '4':
            if ''.join(n[1:4]) in form or ''.join(n[1:6]) == '17500':
                return True
    return False