Implementations of Luhn's Algorithm
Harvard CS50's library for Python (https://github.com/cs50/python-cs50) and for C (https://github.com/cs50/libcs50)
To test the programs, credit card numbers from this link can be used. (https://www.paypalobjects.com/en_US/vhelp/paypalmanager_help/credit_card_numbers.htm)