The Labouchère system, also called the cancellation system or split martingale, is a gambling strategy used in roulette. The user of such a strategy decides before playing how much money they want to win, and writes down a list of positive numbers that sum to the predetermined amount. With each bet, the player stakes an amount equal to the sum of the first and last numbers on the list. If only one number remains, that number is the amount of the stake.
If the bet is successful, the two amounts are removed from the list. If the bet is unsuccessful, the amount lost is appended to the end of the list. This process continues until either the list is completely crossed out, at which point the desired amount of money has been won, or until the player runs out of money to wager. The system is named for British politician and journalist Henry Labouchère, who originally devised the strategy. (資料來源 )
The theory behind this Labouchère system is that, because the player is crossing two numbers off of the list (win) for every number added (loss) the player can complete the list, (crossing out all numbers) thereby winning the desired amount even though the player does not need to win as much as expected for this to occur.
The Labouchère System is meant to be applied to even money Roulette propositions such as Even/Odd, Red/Black or 1–18/19–36. When any of these bets are made in the game of Roulette, a spin resulting in a “0” or “00” results in a loss, so even though the payout is even money, the odds are clearly not 50/50. The Labouchère System attempts to offset these odds. (資料來源 )
