# Why in formula of power of periodic signal is $2N+1$?

Where does $$1$$ come from, like from $$-N$$ to $$N$$ is $$2N$$ so why is $$2N+1$$?

• -N to -1 is N, 1 to N is N, then you need to count the 0 index so all together it’s 2N+1. Just choose an N, write the numbers -N to N down, and count how many you have. Nov 17 '20 at 22:05
• yes i got the idea thank you Jan 12 at 21:33

Isn't $$-N$$ to $$N$$ $$2N+1$$ index in total (you probably missed the 0 here)
$$P = \lim_{N\to\infty} {\frac{1}{2N+1} \sum_{n=-N}^N} \lvert x[n] \rvert^2$$