28BYJ-48 5-Volt Stepper

I was getting about 7RPM using 1,2,3,4 sequence in library.
15RPM with decent torque using 1,3,2,4 in library.
35RPM with your code and more torque!
I can't even stop it with my finger.
The improvement is like night and day.
You have to increase the speed gradually during ~10ms to achieve 35RPM.
Thanks!