Hollandish System

The Hollandish roulette system is a negative progression system (like the Martingale and the Labouchere system, where you increase your bets after a loss to claw back to profit). Like these other systems, this is normally played on the even payout bets (red/black etc).

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The big difference is that The Hollandish is a lower risk system- it is much less aggressive than the Martingale. The main method of "calming things down", is to split your session into mini sessions of 3 spins. This idea of splitting up your bet progression has spawned a number of systems (the Guetting Progression also splits a sequence up, for example).
Instead of increasing your bets after every loss, as you do with the Martingale, in the Hollandish system, you alter your bet after 3 spins. As you can imagine, this has the effect of flattening the betting profile quite a bit. 

Let's say you kick off with a 1 unit bet. Bet 1 three times in a "Hollandish Block". If you win twice or more, then you have won that mini-session- so you would repeat the first betting level on your next mini session.

If you only win 1, or lose all three, then you have lost that mini sessio, and you will need to try and claw back any previous losses by increasing your bet to 3 units a part of a 3 bet block. If, at the end of any mini session, you have less than the bankroll you started with, then you need to move up a stage in the Hollandish progression. You keep going up the stages until you go positive, at which point you drop back to the beginning and re-start.

1 - 3 - 5 - 5 - 7 - 9

Pros
Less aggressive.

Cons
You can still get caught in an increasing bet spiral if your luck is not running your way.
Can be slow to grind through the levels.

Example
Here is an Example of a Hollandish sequence we played recently. Notice, we started on 2 (you can multiple the basic sequence by whatever you want, so 1,3,5,7,9 becomes 2,6,10,14,18 etc.

Here is a numerical example to better explain things:

Bet 2 and lost - Balance -2
Bet 2 and lost - Balance -4
Bet 2 and won- Balance -2
Bet 6 and lost- Balance -8
Bet 6 and won- Balance -2
Bet 6 and lost- Balance -8
Bet 10 and lost- Balance -18
Bet 10 and won- Balance -8
Bet 10 and won- Balance +2 (Start next mini session at your starter bet- in this case 2).