Flatbetting 21 numbers

[ignatus]

Wasn't so bad. (see pic)

How I chose these numbers: Pick that number hit 2 times within 20 spins, until 21 numbers....

[rouletteKEY]

I have so much to say...maybe I'll just leave it at this

I think you were farther ahead by pursuing the single number method you were inquiring about on another thread.

Still trying to help

[Proofreaders2000]

Nice graph Ignatus 

The challenge is you're in a walk-in casino and you're not allowed to use a notepad, just a system from wrote memory.  How could you implement that 21 number strategy?