A riffle shuffle, in which the top half of the deck is placed in the left hand, and cards are then alternatively interleaved from the left and right hands. Using an in-shuffle, a deck originally arranged as 1 2 3 4 5 6 7 8 would become 5 1 6 2 7 3 8 4. The ordering of a deck of 52 cards after an in-shuffle is given by 27, 1, 28, 2, 29, 3, ... (OEIS A059952).

out-shuffle | riffle shuffle