I do something similar. It's hard for me to just dismiss them though. Usually I debate if they hold some truth to them or not. I can never decide, this frustrates me and I begin to repeat some random phrase or do a math pattern. The phrases seem to make it worse, but the math problems help a lot. It requires attention when the numbers get higher so I can't afford to have intrusive thoughts running in the background. I try to do this in my head, but sometimes I end up whispering or holding my ears. Often I rock in place or pinch myself.
When you're going over number sequences, does it ever show externally? Would a random stranger be able to tell?