D'alembert (blackjack)
A betting progression. It is a system where the bettor raises
the bet one unit after each loss and lowers the bet one unit
after each win. A series of numbers equidistant from one another
is established, such as 1, 2, 3, 4. The player starts out by
betting 1 unit. If he wins, he continues to bet one unit. If
he loses, he cancels out the 1 and moves to the 2 and adds one
unit to the last number, now having a series of 2, 3, 4, 5.
At any point in the series where the player wins his bet, he
reduces his bet by one unit. If he wins enough bets to return
to a one unit bet, he starts over. If he loses during the series,
he cancels out the last number he played and adds another number
to the series. This system has many variations. It has never
been proven to win, and in fact, cannot win in any game with
a negative expectation.
