How can I calculate the confidence interval for ACF

Question

I have found multiple sources. One is claiming that the confidence interval is estimated by:

qnorm((1 + ci)/2)/sqrt(x$n.used)

(How is the confidence interval calculated for the ACF function?)

However, I also found this estimator:

(exp(21.96/√(N-3)-1)/(exp(21.96/√(N-3)+1)

https://stackoverflow.com/questions/29996910/significance-level-of-acf-and-pacf-in-r

Does anyone have an idea which one is correct?

Thanks