key-cards Counting hotel key cards References: https://possiblywrong.wordpress.com/2020/10/24/counting-hotel-key-cards/ https://possiblywrong.wordpress.com/2020/02/26/fair-dice-some-isohedra-are-less-fair-than-others/ https://possiblywrong.wordpress.com/2012/09/09/ant-in-the-desert/