It's a bit tricky because velocity and altitude are floored every step, and you can only burn on whole timesteps so you can't necessarily hit the target velocity and altitude in a single burn.

I'm not sure if it's optimal, but this is a 2-burn solution that does 1 burn to hit x=20 and another to hit v>=-14 right afterwards: https://gist.github.com/sgentle/d88dd6fe37e76f9167db24379dc7...