I'm happy to know that you liked the post.

Ok, let's clarify it a little bit.

1. The threads are series of instructions (a.k.a. statements) executed when running a program. The state is the current situation of the variables stored in memory by the program.
2. A program can be determined by the set of operations allowed for that particular program and its initial state (much like how you determine the position of a body at any time if you know the position at t₀ and the explicit expression of the function V(t) in classical mechanics).
3. Changes on states of a program are the result of applying an atomic operation from (A_π) to the previous state. For the initial execution the first operation is made on the initial state, then the second operation is executed over the result of the first operation and so on.
4. The execution of any program (not just concurrent ones) can be thought of as a infinite series of states. Even if a program state is constant, it can be represented as an infinite series of the initial state σ = S₀S₀S₀...
   So there is no such a finite series for a sequential program for a given execution. What do exist is a finite sequence for a partial execution of a program, this fact does not change if the program is sequential or concurrent.

I hope I have given a clearer explanation. If you have more questions make more comments without doubt.

cya.