[pzhon]

Your progression doesn't make sense. When you lose on those 7 numbers, you don't just lose one bet. You lose 2. If you want to come out ahead by one unit on your first win, you need to bet 1, 3, 9, 27, 81, 243. If you lose while placing two bets of size 243, you will end up down 728. This happens with probability (7/19)^6 ~ 1/400. So, with probability 399/400, you win 1 unit, and with probability 1/400, you lose 728 units. You'll lose an average of about 1/4 of a unit per spin of the roulette wheel by using this system.

I don't recommend thinking about martingales a lot. There is no way to add up negative numbers to get a positive number. However, many people have deluded themselves into thinking that this is possible by making a system that is too complicated to understand at a glance.