https://en.wikipedia.org/wiki/Martingale_(betting_system)

It's called Martingale

It's a system where you place bets at odds 2.0 or simmilar and each time you lose, you double your bet in order to recover your losses

So, if your starting bet is 0.001BTC and you lose, in order to recover that loss, you place a 0.002BTC bet, now you've won 0.004BTC and are in overall profit

Sounds good in theory, since the odds of getting 20 reds in a row are around 1 in a million
You place a lot of bets and with each bet placed odds of rolling that 20 red strike are higher and higher, until it eventually happens
And when it does, results are catastrophic
Imagine your bet was 0.001

Bet 1 - 0.001
Bet 2 - 0.002
Bet 3 - 0.004
Bet 4 - 0.008
Bet 5- 0.016
Bet 6- 0.032
Bet 7- 0.064
Bet 8 - 0.128
Bet 9 - 0.256
Bet 10 - 0.512
Bet 11- 1.024
Bet 12 - 2.048
Bet 13- 4.096
Bet 14- 8. 192
Bet 15- 16.384
Bet 16 - 32.768
Bet 17 - 65.536
Bet 18 - 131.072
Bet 19 - 262.144
Bet 20 - 524.288

And you lost a 1000BTC
You don't even have to do 20, you can do 15, I got 16 reds then deposited more to roll 30% of the new deposit and got 17 new reds
Shit happens, stay away from Martingale