Seven Perfect Shuffles Randomize a Deck of Cards. But How Many Sloppy Ones?

Article excerpt

In 1992, mathematicians famously proved that seven “riffle shuffles”, the kind where a player splits a deck of cards into two piles, then uses their thumbs to interleave them back together in a zipperlike motion, are enough to mix up the deck. When Dave Bayer and Persi Diaconis came up with this proof, they also revealed something surprising about what happens along the way: At first… Source